diff --git a/.github/workflows/master.yml b/.github/workflows/master.yml
index bc9d5f8..01b89bc 100644
--- a/.github/workflows/master.yml
+++ b/.github/workflows/master.yml
@@ -13,11 +13,19 @@ jobs:
       MAVEN_CENTRAL_PGP_KEY: ${{ secrets.MAVEN_CENTRAL_PGP_KEY }}
 
     steps:
-      - uses: actions/checkout@v1
-      - uses: gradle/wrapper-validation-action@v1
-      - name: Set up JDK 1.8
-        uses: actions/setup-java@v1
+      - uses: actions/checkout@v4
+      - uses: gradle/actions/wrapper-validation@v3
+      - name: Set up JDK 11
+        uses: actions/setup-java@v4
         with:
-          java-version: '8.0.282'
+          java-version: '11'
+          distribution: 'temurin'
+          check-latest: true
+      # Configure Gradle for optimal use in GiHub Actions, including caching of downloaded dependencies.
+      # See: https://github.com/gradle/actions/blob/main/setup-gradle/README.md
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v4
       - name: build test and publish
         run: ./gradlew assemble && ./gradlew check --info && ./gradlew publishToSonatype closeAndReleaseSonatypeStagingRepository -x check --info --stacktrace
+        env:
+          CI: true
diff --git a/.github/workflows/pull_request.yml b/.github/workflows/pull_request.yml
index 13a366a..f16bf96 100644
--- a/.github/workflows/pull_request.yml
+++ b/.github/workflows/pull_request.yml
@@ -7,15 +7,25 @@ on:
   pull_request:
     branches:
       - master
+      - reactive-streams-branch
+      - '**'
 jobs:
   buildAndTest:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v1
-      - uses: gradle/wrapper-validation-action@v1
-      - name: Set up JDK 1.8
-        uses: actions/setup-java@v1
+      - uses: actions/checkout@v4
+      - uses: gradle/actions/wrapper-validation@v3
+      - name: Set up JDK 11
+        uses: actions/setup-java@v4
         with:
-          java-version: '8.0.282'
+          java-version: '11'
+          distribution: 'temurin'
+          check-latest: true
+      # Configure Gradle for optimal use in GiHub Actions, including caching of downloaded dependencies.
+      # See: https://github.com/gradle/actions/blob/main/setup-gradle/README.md
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v4
       - name: build and test
         run: ./gradlew assemble && ./gradlew check --info --stacktrace
+        env:
+          CI: true
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index b61d755..a574a68 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -17,11 +17,19 @@ jobs:
       RELEASE_VERSION: ${{ github.event.inputs.version }}
 
     steps:
-      - uses: actions/checkout@v1
-      - uses: gradle/wrapper-validation-action@v1
-      - name: Set up JDK 1.8
-        uses: actions/setup-java@v1
+      - uses: actions/checkout@v4
+      - uses: gradle/actions/wrapper-validation@v3
+      - name: Set up JDK 11
+        uses: actions/setup-java@v4
         with:
-          java-version: '8.0.282'
+          java-version: '11'
+          distribution: 'temurin'
+          check-latest: true
+      # Configure Gradle for optimal use in GiHub Actions, including caching of downloaded dependencies.
+      # See: https://github.com/gradle/actions/blob/main/setup-gradle/README.md
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v4
       - name: build test and publish
         run: ./gradlew assemble && ./gradlew check --info && ./gradlew publishToSonatype closeAndReleaseSonatypeStagingRepository -x check --info --stacktrace
+        env:
+          CI: true
diff --git a/README.md b/README.md
index 24a65f6..fbfd620 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,7 @@
 [![Latest Release](https://maven-badges.herokuapp.com/maven-central/com.graphql-java/java-dataloader/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.graphql-java/java-dataloader/) 
 [![Apache licensed](https://img.shields.io/hexpm/l/plug.svg?maxAge=2592000)](https://github.com/graphql-java/java-dataloader/blob/master/LICENSE)
 
-This small and simple utility library is a pure Java 8 port of [Facebook DataLoader](https://github.com/facebook/dataloader). 
+This small and simple utility library is a pure Java 11 port of [Facebook DataLoader](https://github.com/facebook/dataloader). 
 
 It can serve as integral part of your application's data layer to provide a
 consistent API over various back-ends and reduce message communication overhead through batching and caching.
@@ -15,7 +15,7 @@ are resolved independently and, with a true graph of objects, you may be fetchin
 A naive implementation of graphql data fetchers can easily lead to the dreaded  "n+1" fetch problem. 
 
 Most of the code is ported directly from Facebook's reference implementation, with one IMPORTANT adaptation to make
-it work for Java 8. ([more on this below](#manual-dispatching)).
+it work for Java 11. ([more on this below](#manual-dispatching)).
 
 Before reading on, be sure to take a short dive into the
 [original documentation](https://github.com/facebook/dataloader/blob/master/README.md) provided by Lee Byron (@leebyron)
@@ -67,7 +67,7 @@ repositories {
 }
 
 dependencies {
-    compile 'com.graphql-java:java-dataloader: 3.1.0'
+    compile 'com.graphql-java:java-dataloader: 3.3.0'
 }
 ```
 
@@ -286,6 +286,77 @@ For example, let's assume you want to load users from a database, you could prob
         // ...
 ```
 
+### Returning a stream of results from your batch publisher
+
+It may be that your batch loader function can use a [Reactive Streams](https://www.reactive-streams.org/) [Publisher](https://www.reactive-streams.org/reactive-streams-1.0.3-javadoc/org/reactivestreams/Publisher.html), where values are emitted as an asynchronous stream.
+
+For example, let's say you wanted to load many users from a service without forcing the service to load all
+users into its memory (which may exert considerable pressure on it).
+
+A `org.dataloader.BatchPublisher` may be used to load this data:
+
+```java
+        BatchPublisher<Long, User> batchPublisher = new BatchPublisher<Long, User>() {
+            @Override
+            public void load(List<Long> userIds, Subscriber<User> userSubscriber) {
+                Publisher<User> userResults = userManager.streamUsersById(userIds);
+                userResults.subscribe(userSubscriber);
+            }
+        };
+        DataLoader<Long, User> userLoader = DataLoaderFactory.newPublisherDataLoader(batchPublisher);
+
+        // ...
+```
+
+Rather than waiting for all user values to be returned on one batch, this `DataLoader` will complete
+the `CompletableFuture<User>` returned by `Dataloader#load(Long)` as each value is
+published.  
+
+This pattern means that data loader values can (in theory) be satisfied more quickly than if we wait for
+all results in the batch to be retrieved and hence the overall result may finish more quickly.
+
+If an exception is thrown, the remaining futures yet to be completed are completed
+exceptionally.
+
+You *MUST* ensure that the values are streamed in the same order as the keys provided,
+with the same cardinality (i.e. the number of values must match the number of keys).
+
+Failing to do so will result in incorrect data being returned from `DataLoader#load`.
+
+`BatchPublisher` is the reactive version of `BatchLoader`.
+
+
+### Returning a mapped stream of results from your batch publisher
+
+Your publisher may not necessarily return values in the same order in which it processes keys and it 
+may not be able to find a value for each key presented.
+
+For example, let's say your batch publisher function loads user data which is spread across shards,
+with some shards responding more quickly than others.
+
+In instances like these, `org.dataloader.MappedBatchPublisher` can be used.
+
+```java
+        MappedBatchPublisher<Long, User> mappedBatchPublisher = new MappedBatchPublisher<Long, User>() {
+            @Override
+            public void load(Set<Long> userIds, Subscriber<Map.Entry<Long, User>> userEntrySubscriber) {
+                Publisher<Map.Entry<Long, User>> userEntries = userManager.streamUsersById(userIds);
+                userEntries.subscribe(userEntrySubscriber);
+            }
+        };
+        DataLoader<Long, User> userLoader = DataLoaderFactory.newMappedPublisherDataLoader(mappedBatchPublisher);
+
+        // ...
+```
+
+Like the `BatchPublisher`, if an exception is thrown, the remaining futures yet to be completed are completed
+exceptionally.
+
+Unlike the `BatchPublisher`, however, it is not necessary to return values in the same order as the provided keys,
+or even the same number of values.
+
+`MappedBatchPublisher` is the reactive version of `MappedBatchLoader`.
+
 ### Error object is not a thing in a type safe Java world
 
 In the reference JS implementation if the batch loader returns an `Error` object back from the `load()` promise is rejected
@@ -541,6 +612,12 @@ The following is a `BatchLoaderScheduler` that waits 10 milliseconds before invo
                     return scheduledCall.invoke();
                 }).thenCompose(Function.identity());
             }
+
+             @Override
+             public <K> void scheduleBatchPublisher(ScheduledBatchPublisherCall scheduledCall, List<K> keys, BatchLoaderEnvironment environment) {
+                 snooze(10);
+                 scheduledCall.invoke();
+             }
         };
 ```
 
@@ -697,10 +774,10 @@ This library was originally written for use within a [VertX world](http://vertx.
 itself.  All the heavy lifting has been done by this project : [vertx-dataloader](https://github.com/engagingspaces/vertx-dataloader)
 including the extensive testing (which itself came from Facebook).
 
-This particular port was done to reduce the dependency on Vertx and to write a pure Java 8 implementation with no dependencies and also
+This particular port was done to reduce the dependency on Vertx and to write a pure Java 11 implementation with no dependencies and also
 to use the more normative Java CompletableFuture.  
 
-[vertx-core](http://vertx.io/docs/vertx-core/java/) is not a lightweight library by any means so having a pure Java 8 implementation is 
+[vertx-core](http://vertx.io/docs/vertx-core/java/) is not a lightweight library by any means so having a pure Java 11 implementation is 
 very desirable.
 
 
diff --git a/build.gradle b/build.gradle
index f5064ed..70d3918 100644
--- a/build.gradle
+++ b/build.gradle
@@ -3,12 +3,20 @@ import java.text.SimpleDateFormat
 plugins {
     id 'java'
     id 'java-library'
+    id 'jvm-test-suite'
     id 'maven-publish'
     id 'signing'
-	id "biz.aQute.bnd.builder" version "6.2.0"
-    id "io.github.gradle-nexus.publish-plugin" version "1.0.0"
+    id 'groovy'
+    id 'biz.aQute.bnd.builder' version '6.2.0'
+    id 'io.github.gradle-nexus.publish-plugin' version '1.0.0'
+    id 'com.github.ben-manes.versions' version '0.51.0'
 }
 
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(11)
+    }
+}
 
 def getDevelopmentVersion() {
     def output = new StringBuilder()
@@ -25,20 +33,10 @@ def getDevelopmentVersion() {
     version
 }
 
-if (JavaVersion.current() != JavaVersion.VERSION_1_8) {
-    def msg = String.format("This build must be run with java 1.8 - you are running %s - gradle finds the JDK via JAVA_HOME=%s",
-            JavaVersion.current(), System.getenv("JAVA_HOME"))
-    throw new IllegalStateException(msg)
-}
-
-
-sourceCompatibility = 1.8
-targetCompatibility = 1.8
-def slf4jVersion = '1.7.30'
 def releaseVersion = System.env.RELEASE_VERSION
 version = releaseVersion ? releaseVersion : getDevelopmentVersion()
 group = 'com.graphql-java'
-description = 'A pure Java 8 port of Facebook Dataloader'
+description = 'A pure Java 11 port of Facebook Dataloader'
 
 gradle.buildFinished { buildResult ->
     println "*******************************"
@@ -58,47 +56,64 @@ repositories {
     mavenLocal()
 }
 
-apply plugin: 'groovy'
-
 jar {
     manifest {
         attributes('Automatic-Module-Name': 'org.dataloader',
-		'-exportcontents': 'org.dataloader.*',
-		'-removeheaders': 'Private-Package')
+                '-exportcontents': 'org.dataloader.*',
+                '-removeheaders': 'Private-Package')
     }
 }
 
 dependencies {
-    api 'org.slf4j:slf4j-api:' + slf4jVersion
-    testImplementation 'org.slf4j:slf4j-simple:' + slf4jVersion
-    testImplementation 'junit:junit:4.12'
-    testImplementation 'org.awaitility:awaitility:2.0.0'
-    testImplementation 'com.github.ben-manes.caffeine:caffeine:2.9.0'
+    api "org.slf4j:slf4j-api:$slf4j_version"
+    api "org.reactivestreams:reactive-streams:$reactive_streams_version"
 }
 
 task sourcesJar(type: Jar) {
     dependsOn classes
-    classifier 'sources'
+    archiveClassifier.set('sources')
     from sourceSets.main.allSource
 }
 
-task javadocJar(type: Jar, dependsOn: javadoc) {
-    classifier = 'javadoc'
-    from javadoc.destinationDir
-}
-
 javadoc {
     options.encoding = 'UTF-8'
 }
 
+task javadocJar(type: Jar, dependsOn: javadoc) {
+    archiveClassifier.set('javadoc')
+    from javadoc.destinationDir
+}
+
 artifacts {
     archives sourcesJar
     archives javadocJar
 }
 
-test {
-    testLogging {
-        exceptionFormat = 'full'
+testing {
+    suites {
+        test {
+            useJUnitJupiter(junit_version)
+            dependencies {
+                // Testing dependencies
+                implementation platform("org.junit:junit-bom:$junit_version")
+                implementation 'org.junit.jupiter:junit-jupiter-api'
+                implementation 'org.junit.jupiter:junit-jupiter-params'
+                implementation 'org.junit.jupiter:junit-jupiter-engine'
+                implementation "org.slf4j:slf4j-simple:$slf4j_version"
+                implementation "org.awaitility:awaitility:$awaitility_version"
+                implementation "org.hamcrest:hamcrest:$hamcrest_version"
+                implementation "io.projectreactor:reactor-core:$reactor_core_version"
+                implementation "com.github.ben-manes.caffeine:caffeine:$caffeine_version"
+            }
+
+            targets.configureEach {
+                testTask.configure {
+                    testLogging {
+                        exceptionFormat = 'full'
+                    }
+                }
+            }
+        }
     }
 }
 
@@ -117,7 +132,7 @@ publishing {
                 asNode().children().last() + {
                     resolveStrategy = Closure.DELEGATE_FIRST
                     name 'java-dataloader'
-                    description 'A pure Java 8 port of Facebook Dataloader'
+                    description 'A pure Java 11 port of Facebook Dataloader'
                     url 'https://github.com/graphql-java/java-dataloader'
                     inceptionYear '2017'
 
@@ -173,9 +188,15 @@ tasks.withType(PublishToMavenRepository) {
     dependsOn build
 }
 
-
-task myWrapper(type: Wrapper) {
-    gradleVersion = '6.6.1'
-    distributionUrl = "https://services.gradle.org/distributions/gradle-${gradleVersion}-all.zip"
+def isNonStable = { String version ->
+    def stableKeyword = ['RELEASE', 'FINAL', 'GA'].any { it -> version.toUpperCase().contains(it) }
+    def regex = /^[0-9,.v-]+(-r)?$/
+    return !stableKeyword && !(version ==~ regex)
 }
 
+// https://github.com/ben-manes/gradle-versions-plugin
+tasks.named("dependencyUpdates").configure {
+    rejectVersionIf {
+        isNonStable(it.candidate.version)
+    }
+}
\ No newline at end of file
diff --git a/gradle.properties b/gradle.properties
index 0394946..22d5603 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,2 +1,27 @@
+# Project-wide Gradle settings.
+
+# For more details on how to configure your build environment visit
+# http://www.gradle.org/docs/current/userguide/build_environment.html
+
+# Specifies the JVM arguments used for the daemon process.
+# The setting is particularly useful for tweaking memory settings.
+org.gradle.jvmargs=-Xmx4096m
+
+# When configured, Gradle will run in parallel mode.
+# This option should only be used with decoupled projects. More details, visit
+# http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
+org.gradle.parallel=true
+org.gradle.caching=true
+
+# Bespoke settings.
 projectTitle = Java Dataloader
-projectDescription = Port of Facebook Dataloader for Java
\ No newline at end of file
+projectDescription = Port of Facebook Dataloader for Java
+
+# Dependency versions.
+junit_version=5.11.3
+hamcrest_version=2.2
+slf4j_version=1.7.30
+awaitility_version=2.0.0
+reactor_core_version=3.6.6
+caffeine_version=3.1.8
+reactive_streams_version=1.0.3
\ No newline at end of file
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index d2880ba..e2847c8 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.3.2-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.11.1-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/settings.gradle b/settings.gradle
index e69de29..47404e7 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -0,0 +1,21 @@
+plugins {
+    id 'com.gradle.develocity' version '3.19'
+    id 'org.gradle.toolchains.foojay-resolver-convention' version '0.9.0'
+}
+
+develocity {
+    buildScan {
+        final def isCI = System.getenv('CI') != null;
+        termsOfUseUrl = "https://gradle.com/help/legal-terms-of-use"
+        termsOfUseAgree = "yes"
+        publishing.onlyIf { true }
+        tag(isCI ? 'CI' : 'Local')
+        uploadInBackground = !isCI
+    }
+}
+
+dependencyResolutionManagement {
+    repositories {
+        mavenCentral()
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/org/dataloader/BatchPublisher.java b/src/main/java/org/dataloader/BatchPublisher.java
new file mode 100644
index 0000000..c499226
--- /dev/null
+++ b/src/main/java/org/dataloader/BatchPublisher.java
@@ -0,0 +1,36 @@
+package org.dataloader;
+
+import org.reactivestreams.Subscriber;
+
+import java.util.List;
+
+/**
+ * A function that is invoked for batch loading a stream of data values indicated by the provided list of keys.
+ * <p>
+ * The function <b>must</b> call the provided {@link Subscriber} to process the values it has retrieved to allow
+ * the future returned by {@link DataLoader#load(Object)} to complete as soon as the individual value is available
+ * (rather than when all values have been retrieved).
+ * <p>
+ * <b>NOTE:</b> It is <b>required</b> that {@link Subscriber#onNext(Object)} is invoked on each value in the same order as
+ * the provided keys and that you provide a value for every key provided.
+ *
+ * @param <K> type parameter indicating the type of keys to use for data load requests.
+ * @param <V> type parameter indicating the type of values returned
+ * @see BatchLoader for the non-reactive version
+ */
+public interface BatchPublisher<K, V> {
+    /**
+     * Called to batch the provided keys into a stream of values.  You <b>must</b> provide
+     * the same number of values as there as keys, and they <b>must</b> be in the order of the keys.
+     * <p>
+     * The idiomatic approach would be to create a reactive {@link org.reactivestreams.Publisher} that provides
+     * the values given the keys and then subscribe to it with the provided {@link Subscriber}.
+     * <p>
+     * <b>NOTE:</b> It is <b>required</b> that {@link Subscriber#onNext(Object)} is invoked on each value in the same order as
+     * the provided keys and that you provide a value for every key provided.
+     *
+     * @param keys       the collection of keys to load
+     * @param subscriber as values arrive you must call the subscriber for each value
+     */
+    void load(List<K> keys, Subscriber<V> subscriber);
+}
diff --git a/src/main/java/org/dataloader/BatchPublisherWithContext.java b/src/main/java/org/dataloader/BatchPublisherWithContext.java
new file mode 100644
index 0000000..4eadfe9
--- /dev/null
+++ b/src/main/java/org/dataloader/BatchPublisherWithContext.java
@@ -0,0 +1,34 @@
+package org.dataloader;
+
+import org.reactivestreams.Subscriber;
+
+import java.util.List;
+
+/**
+ * This form of {@link BatchPublisher} is given a {@link org.dataloader.BatchLoaderEnvironment} object
+ * that encapsulates the calling context.  A typical use case is passing in security credentials or database details
+ * for example.
+ * <p>
+ * See {@link BatchPublisher} for more details on the design invariants that you must implement in order to
+ * use this interface.
+ */
+public interface BatchPublisherWithContext<K, V> {
+    /**
+     * Called to batch the provided keys into a stream of values.  You <b>must</b> provide
+     * the same number of values as there as keys, and they <b>must</b> be in the order of the keys.
+     * <p>
+     * The idiomatic approach would be to create a reactive {@link org.reactivestreams.Publisher} that provides
+     * the values given the keys and then subscribe to it with the provided {@link Subscriber}.
+     * <p>
+     * <b>NOTE:</b> It is <b>required</b> that {@link Subscriber#onNext(Object)} is invoked on each value in the same order as
+     * the provided keys and that you provide a value for every key provided.
+     * <p>
+     * This is given an environment object to that maybe be useful during the call.  A typical use case
+     * is passing in security credentials or database details for example.
+     *
+     * @param keys        the collection of keys to load
+     * @param subscriber  as values arrive you must call the subscriber for each value
+     * @param environment an environment object that can help with the call
+     */
+    void load(List<K> keys, Subscriber<V> subscriber, BatchLoaderEnvironment environment);
+}
diff --git a/src/main/java/org/dataloader/CacheMap.java b/src/main/java/org/dataloader/CacheMap.java
index 48d0f41..1a4a455 100644
--- a/src/main/java/org/dataloader/CacheMap.java
+++ b/src/main/java/org/dataloader/CacheMap.java
@@ -65,8 +65,7 @@ static <K, V> CacheMap<K, V> simpleMap() {
     /**
      * Gets the specified key from the cache map.
      * <p>
-     * May throw an exception if the key does not exist, depending on the cache map implementation that is used,
-     * so be sure to check {@link CacheMap#containsKey(Object)} first.
+     * May throw an exception if the key does not exist, depending on the cache map implementation that is used.
      *
      * @param key the key to retrieve
      *
diff --git a/src/main/java/org/dataloader/DataLoader.java b/src/main/java/org/dataloader/DataLoader.java
index 1e4ce7d..dc4b726 100644
--- a/src/main/java/org/dataloader/DataLoader.java
+++ b/src/main/java/org/dataloader/DataLoader.java
@@ -25,10 +25,7 @@
 import java.time.Clock;
 import java.time.Duration;
 import java.time.Instant;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.List;
-import java.util.Optional;
+import java.util.*;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.BiConsumer;
 
@@ -574,6 +571,35 @@ public CompletableFuture<List<V>> loadMany(List<K> keys, List<Object> keyContext
         }
     }
 
+    /**
+     * Requests to load the map of data provided by the specified keys asynchronously, and returns a composite future
+     * of the resulting values.
+     * <p>
+     * If batching is enabled (the default), you'll have to call {@link DataLoader#dispatch()} at a later stage to
+     * start batch execution. If you forget this call the future will never be completed (unless already completed,
+     * and returned from cache).
+     * <p>
+     * The key context object may be useful in the batch loader interfaces such as {@link org.dataloader.BatchLoaderWithContext} or
+     * {@link org.dataloader.MappedBatchLoaderWithContext} to help retrieve data.
+     *
+     * @param keysAndContexts the map of keys to their respective contexts
+     *
+     * @return the composite future of the map of keys and values
+     */
+    public CompletableFuture<Map<K, V>> loadMany(Map<K, ?> keysAndContexts) {
+        nonNull(keysAndContexts);
+
+        synchronized (this) {
+            Map<K, CompletableFuture<V>> collect = new HashMap<>(keysAndContexts.size());
+            for (Map.Entry<K, ?> entry : keysAndContexts.entrySet()) {
+                K key = entry.getKey();
+                Object keyContext = entry.getValue();
+                collect.put(key, load(key, keyContext));
+            }
+            return CompletableFutureKit.allOf(collect);
+        }
+    }
+
     /**
      * Dispatches the queued load requests to the batch execution function and returns a promise of the result.
      * <p>
diff --git a/src/main/java/org/dataloader/DataLoaderFactory.java b/src/main/java/org/dataloader/DataLoaderFactory.java
index 013f473..db14f2e 100644
--- a/src/main/java/org/dataloader/DataLoaderFactory.java
+++ b/src/main/java/org/dataloader/DataLoaderFactory.java
@@ -278,6 +278,274 @@ public static <K, V> DataLoader<K, V> newMappedDataLoaderWithTry(MappedBatchLoad
         return mkDataLoader(batchLoadFunction, options);
     }
 
+    /**
+     * Creates new DataLoader with the specified batch loader function and default options
+     * (batching, caching and unlimited batch size).
+     *
+     * @param batchLoadFunction the batch load function to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newPublisherDataLoader(BatchPublisher<K, V> batchLoadFunction) {
+        return newPublisherDataLoader(batchLoadFunction, null);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function with the provided options
+     *
+     * @param batchLoadFunction the batch load function to use
+     * @param options           the options to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newPublisherDataLoader(BatchPublisher<K, V> batchLoadFunction, DataLoaderOptions options) {
+        return mkDataLoader(batchLoadFunction, options);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and default options
+     * (batching, caching and unlimited batch size) where the batch loader function returns a list of
+     * {@link org.dataloader.Try} objects.
+     * <p>
+     * If it's important you to know the exact status of each item in a batch call and whether it threw exceptions then
+     * you can use this form to create the data loader.
+     * <p>
+     * Using Try objects allows you to capture a value returned or an exception that might
+     * have occurred trying to get a value. .
+     *
+     * @param batchLoadFunction the batch load function to use that uses {@link org.dataloader.Try} objects
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newPublisherDataLoaderWithTry(BatchPublisher<K, Try<V>> batchLoadFunction) {
+        return newPublisherDataLoaderWithTry(batchLoadFunction, null);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and with the provided options
+     * where the batch loader function returns a list of
+     * {@link org.dataloader.Try} objects.
+     *
+     * @param batchLoadFunction the batch load function to use that uses {@link org.dataloader.Try} objects
+     * @param options           the options to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     *
+     * @see #newDataLoaderWithTry(BatchLoader)
+     */
+    public static <K, V> DataLoader<K, V> newPublisherDataLoaderWithTry(BatchPublisher<K, Try<V>> batchLoadFunction, DataLoaderOptions options) {
+        return mkDataLoader(batchLoadFunction, options);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and default options
+     * (batching, caching and unlimited batch size).
+     *
+     * @param batchLoadFunction the batch load function to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newPublisherDataLoader(BatchPublisherWithContext<K, V> batchLoadFunction) {
+        return newPublisherDataLoader(batchLoadFunction, null);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function with the provided options
+     *
+     * @param batchLoadFunction the batch load function to use
+     * @param options           the options to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newPublisherDataLoader(BatchPublisherWithContext<K, V> batchLoadFunction, DataLoaderOptions options) {
+        return mkDataLoader(batchLoadFunction, options);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and default options
+     * (batching, caching and unlimited batch size) where the batch loader function returns a list of
+     * {@link org.dataloader.Try} objects.
+     * <p>
+     * If it's important you to know the exact status of each item in a batch call and whether it threw exceptions then
+     * you can use this form to create the data loader.
+     * <p>
+     * Using Try objects allows you to capture a value returned or an exception that might
+     * have occurred trying to get a value. .
+     *
+     * @param batchLoadFunction the batch load function to use that uses {@link org.dataloader.Try} objects
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newPublisherDataLoaderWithTry(BatchPublisherWithContext<K, Try<V>> batchLoadFunction) {
+        return newPublisherDataLoaderWithTry(batchLoadFunction, null);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and with the provided options
+     * where the batch loader function returns a list of
+     * {@link org.dataloader.Try} objects.
+     *
+     * @param batchLoadFunction the batch load function to use that uses {@link org.dataloader.Try} objects
+     * @param options           the options to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     *
+     * @see #newPublisherDataLoaderWithTry(BatchPublisher)
+     */
+    public static <K, V> DataLoader<K, V> newPublisherDataLoaderWithTry(BatchPublisherWithContext<K, Try<V>> batchLoadFunction, DataLoaderOptions options) {
+        return mkDataLoader(batchLoadFunction, options);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and default options
+     * (batching, caching and unlimited batch size).
+     *
+     * @param batchLoadFunction the batch load function to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newMappedPublisherDataLoader(MappedBatchPublisher<K, V> batchLoadFunction) {
+        return newMappedPublisherDataLoader(batchLoadFunction, null);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function with the provided options
+     *
+     * @param batchLoadFunction the batch load function to use
+     * @param options           the options to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newMappedPublisherDataLoader(MappedBatchPublisher<K, V> batchLoadFunction, DataLoaderOptions options) {
+        return mkDataLoader(batchLoadFunction, options);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and default options
+     * (batching, caching and unlimited batch size) where the batch loader function returns a list of
+     * {@link org.dataloader.Try} objects.
+     * <p>
+     * If it's important you to know the exact status of each item in a batch call and whether it threw exceptions then
+     * you can use this form to create the data loader.
+     * <p>
+     * Using Try objects allows you to capture a value returned or an exception that might
+     * have occurred trying to get a value. .
+     *
+     * @param batchLoadFunction the batch load function to use that uses {@link org.dataloader.Try} objects
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newMappedPublisherDataLoaderWithTry(MappedBatchPublisher<K, Try<V>> batchLoadFunction) {
+        return newMappedPublisherDataLoaderWithTry(batchLoadFunction, null);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and with the provided options
+     * where the batch loader function returns a list of
+     * {@link org.dataloader.Try} objects.
+     *
+     * @param batchLoadFunction the batch load function to use that uses {@link org.dataloader.Try} objects
+     * @param options           the options to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     *
+     * @see #newDataLoaderWithTry(BatchLoader)
+     */
+    public static <K, V> DataLoader<K, V> newMappedPublisherDataLoaderWithTry(MappedBatchPublisher<K, Try<V>> batchLoadFunction, DataLoaderOptions options) {
+        return mkDataLoader(batchLoadFunction, options);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and default options
+     * (batching, caching and unlimited batch size).
+     *
+     * @param batchLoadFunction the batch load function to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newMappedPublisherDataLoader(MappedBatchPublisherWithContext<K, V> batchLoadFunction) {
+        return newMappedPublisherDataLoader(batchLoadFunction, null);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function with the provided options
+     *
+     * @param batchLoadFunction the batch load function to use
+     * @param options           the options to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newMappedPublisherDataLoader(MappedBatchPublisherWithContext<K, V> batchLoadFunction, DataLoaderOptions options) {
+        return mkDataLoader(batchLoadFunction, options);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and default options
+     * (batching, caching and unlimited batch size) where the batch loader function returns a list of
+     * {@link org.dataloader.Try} objects.
+     * <p>
+     * If it's important you to know the exact status of each item in a batch call and whether it threw exceptions then
+     * you can use this form to create the data loader.
+     * <p>
+     * Using Try objects allows you to capture a value returned or an exception that might
+     * have occurred trying to get a value. .
+     *
+     * @param batchLoadFunction the batch load function to use that uses {@link org.dataloader.Try} objects
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     */
+    public static <K, V> DataLoader<K, V> newMappedPublisherDataLoaderWithTry(MappedBatchPublisherWithContext<K, Try<V>> batchLoadFunction) {
+        return newMappedPublisherDataLoaderWithTry(batchLoadFunction, null);
+    }
+
+    /**
+     * Creates new DataLoader with the specified batch loader function and with the provided options
+     * where the batch loader function returns a list of
+     * {@link org.dataloader.Try} objects.
+     *
+     * @param batchLoadFunction the batch load function to use that uses {@link org.dataloader.Try} objects
+     * @param options           the options to use
+     * @param <K>               the key type
+     * @param <V>               the value type
+     *
+     * @return a new DataLoader
+     *
+     * @see #newMappedPublisherDataLoaderWithTry(MappedBatchPublisher)
+     */
+    public static <K, V> DataLoader<K, V> newMappedPublisherDataLoaderWithTry(MappedBatchPublisherWithContext<K, Try<V>> batchLoadFunction, DataLoaderOptions options) {
+        return mkDataLoader(batchLoadFunction, options);
+    }
+
     static <K, V> DataLoader<K, V> mkDataLoader(Object batchLoadFunction, DataLoaderOptions options) {
         return new DataLoader<>(batchLoadFunction, options);
     }
diff --git a/src/main/java/org/dataloader/DataLoaderHelper.java b/src/main/java/org/dataloader/DataLoaderHelper.java
index 1e48a94..9cd38d6 100644
--- a/src/main/java/org/dataloader/DataLoaderHelper.java
+++ b/src/main/java/org/dataloader/DataLoaderHelper.java
@@ -3,6 +3,7 @@
 import org.dataloader.annotations.GuardedBy;
 import org.dataloader.annotations.Internal;
 import org.dataloader.impl.CompletableFutureKit;
+import org.dataloader.reactive.ReactiveSupport;
 import org.dataloader.scheduler.BatchLoaderScheduler;
 import org.dataloader.stats.StatisticsCollector;
 import org.dataloader.stats.context.IncrementBatchLoadCountByStatisticsContext;
@@ -10,6 +11,7 @@
 import org.dataloader.stats.context.IncrementCacheHitCountStatisticsContext;
 import org.dataloader.stats.context.IncrementLoadCountStatisticsContext;
 import org.dataloader.stats.context.IncrementLoadErrorCountStatisticsContext;
+import org.reactivestreams.Subscriber;
 
 import java.time.Clock;
 import java.time.Instant;
@@ -110,9 +112,13 @@ Optional<CompletableFuture<V>> getIfPresent(K key) {
             boolean cachingEnabled = loaderOptions.cachingEnabled();
             if (cachingEnabled) {
                 Object cacheKey = getCacheKey(nonNull(key));
-                if (futureCache.containsKey(cacheKey)) {
-                    stats.incrementCacheHitCount(new IncrementCacheHitCountStatisticsContext<>(key));
-                    return Optional.of(futureCache.get(cacheKey));
+                try {
+                    CompletableFuture<V> cacheValue = futureCache.get(cacheKey);
+                    if (cacheValue != null) {
+                        stats.incrementCacheHitCount(new IncrementCacheHitCountStatisticsContext<>(key));
+                        return Optional.of(cacheValue);
+                    }
+                } catch (Exception ignored) {
                 }
             }
         }
@@ -148,11 +154,13 @@ CompletableFuture<V> load(K key, Object loadContext) {
         }
     }
 
+    @SuppressWarnings("unchecked")
     Object getCacheKey(K key) {
         return loaderOptions.cacheKeyFunction().isPresent() ?
                 loaderOptions.cacheKeyFunction().get().getKey(key) : key;
     }
 
+    @SuppressWarnings("unchecked")
     Object getCacheKeyWithContext(K key, Object context) {
         return loaderOptions.cacheKeyFunction().isPresent() ?
                 loaderOptions.cacheKeyFunction().get().getKeyWithContext(key, context) : key;
@@ -237,10 +245,14 @@ private CompletableFuture<List<V>> sliceIntoBatchesOfBatches(List<K> keys, List<
     @SuppressWarnings("unchecked")
     private CompletableFuture<List<V>> dispatchQueueBatch(List<K> keys, List<Object> callContexts, List<CompletableFuture<V>> queuedFutures) {
         stats.incrementBatchLoadCountBy(keys.size(), new IncrementBatchLoadCountByStatisticsContext<>(keys, callContexts));
-        CompletableFuture<List<V>> batchLoad = invokeLoader(keys, callContexts, loaderOptions.cachingEnabled());
+        CompletableFuture<List<V>> batchLoad = invokeLoader(keys, callContexts, queuedFutures, loaderOptions.cachingEnabled());
         return batchLoad
                 .thenApply(values -> {
                     assertResultSize(keys, values);
+                    if (isPublisher() || isMappedPublisher()) {
+                        // We have already completed the queued futures by the time the overall batchLoad future has completed.
+                        return values;
+                    }
 
                     List<K> clearCacheKeys = new ArrayList<>();
                     for (int idx = 0; idx < queuedFutures.size(); idx++) {
@@ -307,10 +319,14 @@ private void possiblyClearCacheEntriesOnExceptions(List<K> keys) {
     private CompletableFuture<V> loadFromCache(K key, Object loadContext, boolean batchingEnabled) {
         final Object cacheKey = loadContext == null ? getCacheKey(key) : getCacheKeyWithContext(key, loadContext);
 
-        if (futureCache.containsKey(cacheKey)) {
-            // We already have a promise for this key, no need to check value cache or queue up load
-            stats.incrementCacheHitCount(new IncrementCacheHitCountStatisticsContext<>(key, loadContext));
-            return futureCache.get(cacheKey);
+        try {
+            CompletableFuture<V> cacheValue = futureCache.get(cacheKey);
+            if (cacheValue != null) {
+                // We already have a promise for this key, no need to check value cache or queue up load
+                stats.incrementCacheHitCount(new IncrementCacheHitCountStatisticsContext<>(key, loadContext));
+                return cacheValue;
+            }
+        } catch (Exception ignored) {
         }
 
         CompletableFuture<V> loadCallFuture = queueOrInvokeLoader(key, loadContext, batchingEnabled, true);
@@ -334,14 +350,15 @@ private CompletableFuture<V> queueOrInvokeLoader(K key, Object loadContext, bool
     CompletableFuture<V> invokeLoaderImmediately(K key, Object keyContext, boolean cachingEnabled) {
         List<K> keys = singletonList(key);
         List<Object> keyContexts = singletonList(keyContext);
-        return invokeLoader(keys, keyContexts, cachingEnabled)
+        List<CompletableFuture<V>> queuedFutures = singletonList(new CompletableFuture<>());
+        return invokeLoader(keys, keyContexts, queuedFutures, cachingEnabled)
                 .thenApply(list -> list.get(0))
                 .toCompletableFuture();
     }
 
-    CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts, boolean cachingEnabled) {
+    CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts, List<CompletableFuture<V>> queuedFutures, boolean cachingEnabled) {
         if (!cachingEnabled) {
-            return invokeLoader(keys, keyContexts);
+            return invokeLoader(keys, keyContexts, queuedFutures);
         }
         CompletableFuture<List<Try<V>>> cacheCallCF = getFromValueCache(keys);
         return cacheCallCF.thenCompose(cachedValues -> {
@@ -352,6 +369,7 @@ CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts,
             List<Integer> missedKeyIndexes = new ArrayList<>();
             List<K> missedKeys = new ArrayList<>();
             List<Object> missedKeyContexts = new ArrayList<>();
+            List<CompletableFuture<V>> missedQueuedFutures = new ArrayList<>();
 
             // if they return a ValueCachingNotSupported exception then we insert this special marker value, and it
             // means it's a total miss, we need to get all these keys via the batch loader
@@ -361,6 +379,7 @@ CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts,
                     missedKeyIndexes.add(i);
                     missedKeys.add(keys.get(i));
                     missedKeyContexts.add(keyContexts.get(i));
+                    missedQueuedFutures.add(queuedFutures.get(i));
                 }
             } else {
                 assertState(keys.size() == cachedValues.size(), () -> "The size of the cached values MUST be the same size as the key list");
@@ -385,7 +404,7 @@ CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts,
                 // we missed some keys from cache, so send them to the batch loader
                 // and then fill in their values
                 //
-                CompletableFuture<List<V>> batchLoad = invokeLoader(missedKeys, missedKeyContexts);
+                CompletableFuture<List<V>> batchLoad = invokeLoader(missedKeys, missedKeyContexts, missedQueuedFutures);
                 return batchLoad.thenCompose(missedValues -> {
                     assertResultSize(missedKeys, missedValues);
 
@@ -404,8 +423,7 @@ CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts,
         });
     }
 
-
-    CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts) {
+    CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts, List<CompletableFuture<V>> queuedFutures) {
         CompletableFuture<List<V>> batchLoad;
         try {
             Object context = loaderOptions.getBatchLoaderContextProvider().getContext();
@@ -413,6 +431,10 @@ CompletableFuture<List<V>> invokeLoader(List<K> keys, List<Object> keyContexts)
                     .context(context).keyContexts(keys, keyContexts).build();
             if (isMapLoader()) {
                 batchLoad = invokeMapBatchLoader(keys, environment);
+            } else if (isPublisher()) {
+                batchLoad = invokeBatchPublisher(keys, keyContexts, queuedFutures, environment);
+            } else if (isMappedPublisher()) {
+                batchLoad = invokeMappedBatchPublisher(keys, keyContexts, queuedFutures, environment);
             } else {
                 batchLoad = invokeListBatchLoader(keys, environment);
             }
@@ -484,10 +506,72 @@ private CompletableFuture<List<V>> invokeMapBatchLoader(List<K> keys, BatchLoade
         });
     }
 
+    private CompletableFuture<List<V>> invokeBatchPublisher(List<K> keys, List<Object> keyContexts, List<CompletableFuture<V>> queuedFutures, BatchLoaderEnvironment environment) {
+        CompletableFuture<List<V>> loadResult = new CompletableFuture<>();
+        Subscriber<V> subscriber = ReactiveSupport.batchSubscriber(loadResult, keys, keyContexts, queuedFutures, helperIntegration());
+
+        BatchLoaderScheduler batchLoaderScheduler = loaderOptions.getBatchLoaderScheduler();
+        if (batchLoadFunction instanceof BatchPublisherWithContext) {
+            //noinspection unchecked
+            BatchPublisherWithContext<K, V> loadFunction = (BatchPublisherWithContext<K, V>) batchLoadFunction;
+            if (batchLoaderScheduler != null) {
+                BatchLoaderScheduler.ScheduledBatchPublisherCall loadCall = () -> loadFunction.load(keys, subscriber, environment);
+                batchLoaderScheduler.scheduleBatchPublisher(loadCall, keys, environment);
+            } else {
+                loadFunction.load(keys, subscriber, environment);
+            }
+        } else {
+            //noinspection unchecked
+            BatchPublisher<K, V> loadFunction = (BatchPublisher<K, V>) batchLoadFunction;
+            if (batchLoaderScheduler != null) {
+                BatchLoaderScheduler.ScheduledBatchPublisherCall loadCall = () -> loadFunction.load(keys, subscriber);
+                batchLoaderScheduler.scheduleBatchPublisher(loadCall, keys, null);
+            } else {
+                loadFunction.load(keys, subscriber);
+            }
+        }
+        return loadResult;
+    }
+
+    private CompletableFuture<List<V>> invokeMappedBatchPublisher(List<K> keys, List<Object> keyContexts, List<CompletableFuture<V>> queuedFutures, BatchLoaderEnvironment environment) {
+        CompletableFuture<List<V>> loadResult = new CompletableFuture<>();
+        Subscriber<Map.Entry<K, V>> subscriber = ReactiveSupport.mappedBatchSubscriber(loadResult, keys, keyContexts, queuedFutures, helperIntegration());
+        Set<K> setOfKeys = new LinkedHashSet<>(keys);
+        BatchLoaderScheduler batchLoaderScheduler = loaderOptions.getBatchLoaderScheduler();
+        if (batchLoadFunction instanceof MappedBatchPublisherWithContext) {
+            //noinspection unchecked
+            MappedBatchPublisherWithContext<K, V> loadFunction = (MappedBatchPublisherWithContext<K, V>) batchLoadFunction;
+            if (batchLoaderScheduler != null) {
+                BatchLoaderScheduler.ScheduledBatchPublisherCall loadCall = () -> loadFunction.load(keys, subscriber, environment);
+                batchLoaderScheduler.scheduleBatchPublisher(loadCall, keys, environment);
+            } else {
+                loadFunction.load(keys, subscriber, environment);
+            }
+        } else {
+            //noinspection unchecked
+            MappedBatchPublisher<K, V> loadFunction = (MappedBatchPublisher<K, V>) batchLoadFunction;
+            if (batchLoaderScheduler != null) {
+                BatchLoaderScheduler.ScheduledBatchPublisherCall loadCall = () -> loadFunction.load(setOfKeys, subscriber);
+                batchLoaderScheduler.scheduleBatchPublisher(loadCall, keys, null);
+            } else {
+                loadFunction.load(setOfKeys, subscriber);
+            }
+        }
+        return loadResult;
+    }
+
     private boolean isMapLoader() {
         return batchLoadFunction instanceof MappedBatchLoader || batchLoadFunction instanceof MappedBatchLoaderWithContext;
     }
 
+    private boolean isPublisher() {
+        return batchLoadFunction instanceof BatchPublisher;
+    }
+
+    private boolean isMappedPublisher() {
+        return batchLoadFunction instanceof MappedBatchPublisher;
+    }
+
     int dispatchDepth() {
         synchronized (dataLoader) {
             return loaderQueue.size();
@@ -538,4 +622,23 @@ private CompletableFuture<List<V>> setToValueCache(List<V> assembledValues, List
     private static <T> DispatchResult<T> emptyDispatchResult() {
         return (DispatchResult<T>) EMPTY_DISPATCH_RESULT;
     }
+
+    private ReactiveSupport.HelperIntegration<K> helperIntegration() {
+        return new ReactiveSupport.HelperIntegration<>() {
+            @Override
+            public StatisticsCollector getStats() {
+                return stats;
+            }
+
+            @Override
+            public void clearCacheView(K key) {
+                dataLoader.clear(key);
+            }
+
+            @Override
+            public void clearCacheEntriesOnExceptions(List<K> keys) {
+                possiblyClearCacheEntriesOnExceptions(keys);
+            }
+        };
+    }
 }
diff --git a/src/main/java/org/dataloader/MappedBatchPublisher.java b/src/main/java/org/dataloader/MappedBatchPublisher.java
new file mode 100644
index 0000000..754ee52
--- /dev/null
+++ b/src/main/java/org/dataloader/MappedBatchPublisher.java
@@ -0,0 +1,30 @@
+package org.dataloader;
+
+import org.reactivestreams.Subscriber;
+
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * A function that is invoked for batch loading a stream of data values indicated by the provided list of keys.
+ * <p>
+ * The function <b>must</b> call the provided {@link Subscriber} to process the key/value pairs it has retrieved to allow
+ * the future returned by {@link DataLoader#load(Object)} to complete as soon as the individual value is available
+ * (rather than when all values have been retrieved).
+ *
+ * @param <K> type parameter indicating the type of keys to use for data load requests.
+ * @param <V> type parameter indicating the type of values returned
+ * @see MappedBatchLoader for the non-reactive version
+ */
+public interface MappedBatchPublisher<K, V> {
+    /**
+     * Called to batch the provided keys into a stream of map entries of keys and values.
+     * <p>
+     * The idiomatic approach would be to create a reactive {@link org.reactivestreams.Publisher} that provides
+     * the values given the keys and then subscribe to it with the provided {@link Subscriber}.
+     *
+     * @param keys       the collection of keys to load
+     * @param subscriber as values arrive you must call the subscriber for each value
+     */
+    void load(Set<K> keys, Subscriber<Map.Entry<K, V>> subscriber);
+}
diff --git a/src/main/java/org/dataloader/MappedBatchPublisherWithContext.java b/src/main/java/org/dataloader/MappedBatchPublisherWithContext.java
new file mode 100644
index 0000000..2e94152
--- /dev/null
+++ b/src/main/java/org/dataloader/MappedBatchPublisherWithContext.java
@@ -0,0 +1,32 @@
+package org.dataloader;
+
+import org.reactivestreams.Subscriber;
+
+import java.util.List;
+import java.util.Map;
+
+/**
+ * This form of {@link MappedBatchPublisher} is given a {@link org.dataloader.BatchLoaderEnvironment} object
+ * that encapsulates the calling context.  A typical use case is passing in security credentials or database details
+ * for example.
+ * <p>
+ * See {@link MappedBatchPublisher} for more details on the design invariants that you must implement in order to
+ * use this interface.
+ */
+public interface MappedBatchPublisherWithContext<K, V> {
+
+    /**
+     * Called to batch the provided keys into a stream of map entries of keys and values.
+     * <p>
+     * The idiomatic approach would be to create a reactive {@link org.reactivestreams.Publisher} that provides
+     * the values given the keys and then subscribe to it with the provided {@link Subscriber}.
+     * <p>
+     * This is given an environment object to that maybe be useful during the call.  A typical use case
+     * is passing in security credentials or database details for example.
+     *
+     * @param keys        the collection of keys to load
+     * @param subscriber  as values arrive you must call the subscriber for each value
+     * @param environment an environment object that can help with the call
+     */
+    void load(List<K> keys, Subscriber<Map.Entry<K, V>> subscriber, BatchLoaderEnvironment environment);
+}
diff --git a/src/main/java/org/dataloader/impl/CompletableFutureKit.java b/src/main/java/org/dataloader/impl/CompletableFutureKit.java
index 2b94d10..ebc35ec 100644
--- a/src/main/java/org/dataloader/impl/CompletableFutureKit.java
+++ b/src/main/java/org/dataloader/impl/CompletableFutureKit.java
@@ -3,8 +3,10 @@
 import org.dataloader.annotations.Internal;
 
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
+import java.util.stream.Collectors;
 
 import static java.util.stream.Collectors.toList;
 
@@ -48,10 +50,21 @@ public static <V> boolean failed(CompletableFuture<V> future) {
     }
 
     public static <T> CompletableFuture<List<T>> allOf(List<CompletableFuture<T>> cfs) {
-        return CompletableFuture.allOf(cfs.toArray(new CompletableFuture[0]))
+        return CompletableFuture.allOf(cfs.toArray(CompletableFuture[]::new))
                 .thenApply(v -> cfs.stream()
                         .map(CompletableFuture::join)
                         .collect(toList())
                 );
     }
+
+    public static <K, V> CompletableFuture<Map<K, V>> allOf(Map<K, CompletableFuture<V>> cfs) {
+        return CompletableFuture.allOf(cfs.values().toArray(CompletableFuture[]::new))
+                .thenApply(v -> cfs.entrySet().stream()
+                        .collect(
+                                Collectors.toMap(
+                                        Map.Entry::getKey,
+                                        task -> task.getValue().join())
+                        )
+                );
+    }
 }
diff --git a/src/main/java/org/dataloader/reactive/AbstractBatchSubscriber.java b/src/main/java/org/dataloader/reactive/AbstractBatchSubscriber.java
new file mode 100644
index 0000000..c2f5438
--- /dev/null
+++ b/src/main/java/org/dataloader/reactive/AbstractBatchSubscriber.java
@@ -0,0 +1,104 @@
+package org.dataloader.reactive;
+
+import org.dataloader.Try;
+import org.dataloader.stats.context.IncrementBatchLoadExceptionCountStatisticsContext;
+import org.dataloader.stats.context.IncrementLoadErrorCountStatisticsContext;
+import org.reactivestreams.Subscriber;
+import org.reactivestreams.Subscription;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionException;
+
+import static org.dataloader.impl.Assertions.assertState;
+
+/**
+ * The base class for our reactive subscriber support
+ *
+ * @param <T> for two
+ */
+abstract class AbstractBatchSubscriber<K, V, T> implements Subscriber<T> {
+
+    final CompletableFuture<List<V>> valuesFuture;
+    final List<K> keys;
+    final List<Object> callContexts;
+    final List<CompletableFuture<V>> queuedFutures;
+    final ReactiveSupport.HelperIntegration<K> helperIntegration;
+
+    List<K> clearCacheKeys = new ArrayList<>();
+    List<V> completedValues = new ArrayList<>();
+    boolean onErrorCalled = false;
+    boolean onCompleteCalled = false;
+
+    AbstractBatchSubscriber(
+            CompletableFuture<List<V>> valuesFuture,
+            List<K> keys,
+            List<Object> callContexts,
+            List<CompletableFuture<V>> queuedFutures,
+            ReactiveSupport.HelperIntegration<K> helperIntegration
+    ) {
+        this.valuesFuture = valuesFuture;
+        this.keys = keys;
+        this.callContexts = callContexts;
+        this.queuedFutures = queuedFutures;
+        this.helperIntegration = helperIntegration;
+    }
+
+    @Override
+    public void onSubscribe(Subscription subscription) {
+        subscription.request(keys.size());
+    }
+
+    @Override
+    public void onNext(T v) {
+        assertState(!onErrorCalled, () -> "onError has already been called; onNext may not be invoked.");
+        assertState(!onCompleteCalled, () -> "onComplete has already been called; onNext may not be invoked.");
+    }
+
+    @Override
+    public void onComplete() {
+        assertState(!onErrorCalled, () -> "onError has already been called; onComplete may not be invoked.");
+        onCompleteCalled = true;
+    }
+
+    @Override
+    public void onError(Throwable throwable) {
+        assertState(!onCompleteCalled, () -> "onComplete has already been called; onError may not be invoked.");
+        onErrorCalled = true;
+
+        helperIntegration.getStats().incrementBatchLoadExceptionCount(new IncrementBatchLoadExceptionCountStatisticsContext<>(keys, callContexts));
+    }
+
+    /*
+     * A value has arrived - how do we complete the future that's associated with it in a common way
+     */
+    void onNextValue(K key, V value, Object callContext, List<CompletableFuture<V>> futures) {
+        if (value instanceof Try) {
+            // we allow the batch loader to return a Try so we can better represent a computation
+            // that might have worked or not.
+            //noinspection unchecked
+            Try<V> tryValue = (Try<V>) value;
+            if (tryValue.isSuccess()) {
+                futures.forEach(f -> f.complete(tryValue.get()));
+            } else {
+                helperIntegration.getStats().incrementLoadErrorCount(new IncrementLoadErrorCountStatisticsContext<>(key, callContext));
+                futures.forEach(f -> f.completeExceptionally(tryValue.getThrowable()));
+                clearCacheKeys.add(key);
+            }
+        } else {
+            futures.forEach(f -> f.complete(value));
+        }
+    }
+
+    Throwable unwrapThrowable(Throwable ex) {
+        if (ex instanceof CompletionException) {
+            ex = ex.getCause();
+        }
+        return ex;
+    }
+
+    void possiblyClearCacheEntriesOnExceptions() {
+        helperIntegration.clearCacheEntriesOnExceptions(clearCacheKeys);
+    }
+}
diff --git a/src/main/java/org/dataloader/reactive/BatchSubscriberImpl.java b/src/main/java/org/dataloader/reactive/BatchSubscriberImpl.java
new file mode 100644
index 0000000..d0b8110
--- /dev/null
+++ b/src/main/java/org/dataloader/reactive/BatchSubscriberImpl.java
@@ -0,0 +1,86 @@
+package org.dataloader.reactive;
+
+import org.dataloader.impl.DataLoaderAssertionException;
+
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+
+/**
+ * This class can be used to subscribe to a {@link org.reactivestreams.Publisher} and then
+ * have the values it receives complete the data loader keys.  The keys and values must be
+ * in index order.
+ * <p>
+ * This is a reactive version of {@link org.dataloader.BatchLoader}
+ *
+ * @param <K> the type of keys
+ * @param <V> the type of values
+ */
+class BatchSubscriberImpl<K, V> extends AbstractBatchSubscriber<K, V, V> {
+
+    private int idx = 0;
+
+    BatchSubscriberImpl(
+            CompletableFuture<List<V>> valuesFuture,
+            List<K> keys,
+            List<Object> callContexts,
+            List<CompletableFuture<V>> queuedFutures,
+            ReactiveSupport.HelperIntegration<K> helperIntegration
+    ) {
+        super(valuesFuture, keys, callContexts, queuedFutures, helperIntegration);
+    }
+
+    // onNext may be called by multiple threads - for the time being, we pass 'synchronized' to guarantee
+    // correctness (at the cost of speed).
+    @Override
+    public synchronized void onNext(V value) {
+        super.onNext(value);
+
+        if (idx >= keys.size()) {
+            // hang on they have given us more values than we asked for in keys
+            // we cant handle this
+            return;
+        }
+        K key = keys.get(idx);
+        Object callContext = callContexts.get(idx);
+        CompletableFuture<V> future = queuedFutures.get(idx);
+        onNextValue(key, value, callContext, List.of(future));
+
+        completedValues.add(value);
+        idx++;
+    }
+
+
+    @Override
+    public synchronized void onComplete() {
+        super.onComplete();
+        if (keys.size() != completedValues.size()) {
+            // we have more or less values than promised
+            // we will go through all the outstanding promises and mark those that
+            // have not finished as failed
+            for (CompletableFuture<V> queuedFuture : queuedFutures) {
+                if (!queuedFuture.isDone()) {
+                    queuedFuture.completeExceptionally(new DataLoaderAssertionException("The size of the promised values MUST be the same size as the key list"));
+                }
+            }
+        }
+        possiblyClearCacheEntriesOnExceptions();
+        valuesFuture.complete(completedValues);
+    }
+
+    @Override
+    public synchronized void onError(Throwable ex) {
+        super.onError(ex);
+        ex = unwrapThrowable(ex);
+        // Set the remaining keys to the exception.
+        for (int i = idx; i < queuedFutures.size(); i++) {
+            K key = keys.get(i);
+            CompletableFuture<V> future = queuedFutures.get(i);
+            if (!future.isDone()) {
+                future.completeExceptionally(ex);
+                // clear any cached view of this key because it failed
+                helperIntegration.clearCacheView(key);
+            }
+        }
+        valuesFuture.completeExceptionally(ex);
+    }
+}
diff --git a/src/main/java/org/dataloader/reactive/MappedBatchSubscriberImpl.java b/src/main/java/org/dataloader/reactive/MappedBatchSubscriberImpl.java
new file mode 100644
index 0000000..d56efa0
--- /dev/null
+++ b/src/main/java/org/dataloader/reactive/MappedBatchSubscriberImpl.java
@@ -0,0 +1,103 @@
+package org.dataloader.reactive;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+
+/**
+ * This class can be used to subscribe to a {@link org.reactivestreams.Publisher} and then
+ * have the values it receives complete the data loader keys in a map lookup fashion.
+ * <p>
+ * This is a reactive version of {@link org.dataloader.MappedBatchLoader}
+ *
+ * @param <K> the type of keys
+ * @param <V> the type of values
+ */
+class MappedBatchSubscriberImpl<K, V> extends AbstractBatchSubscriber<K, V, Map.Entry<K, V>> {
+
+    private final Map<K, Object> callContextByKey;
+    private final Map<K, List<CompletableFuture<V>>> queuedFuturesByKey;
+    private final Map<K, V> completedValuesByKey = new HashMap<>();
+
+
+    MappedBatchSubscriberImpl(
+            CompletableFuture<List<V>> valuesFuture,
+            List<K> keys,
+            List<Object> callContexts,
+            List<CompletableFuture<V>> queuedFutures,
+            ReactiveSupport.HelperIntegration<K> helperIntegration
+    ) {
+        super(valuesFuture, keys, callContexts, queuedFutures, helperIntegration);
+        this.callContextByKey = new HashMap<>();
+        this.queuedFuturesByKey = new HashMap<>();
+        for (int idx = 0; idx < queuedFutures.size(); idx++) {
+            K key = keys.get(idx);
+            Object callContext = callContexts.get(idx);
+            CompletableFuture<V> queuedFuture = queuedFutures.get(idx);
+            callContextByKey.put(key, callContext);
+            queuedFuturesByKey.computeIfAbsent(key, k -> new ArrayList<>()).add(queuedFuture);
+        }
+    }
+
+
+    @Override
+    public synchronized void onNext(Map.Entry<K, V> entry) {
+        super.onNext(entry);
+        K key = entry.getKey();
+        V value = entry.getValue();
+
+        Object callContext = callContextByKey.get(key);
+        List<CompletableFuture<V>> futures = queuedFuturesByKey.getOrDefault(key, List.of());
+
+        onNextValue(key, value, callContext, futures);
+
+        // did we have an actual key for this value - ignore it if they send us one outside the key set
+        if (!futures.isEmpty()) {
+            completedValuesByKey.put(key, value);
+        }
+    }
+
+    @Override
+    public synchronized void onComplete() {
+        super.onComplete();
+
+        possiblyClearCacheEntriesOnExceptions();
+        List<V> values = new ArrayList<>(keys.size());
+        for (K key : keys) {
+            V value = completedValuesByKey.get(key);
+            values.add(value);
+
+            List<CompletableFuture<V>> futures = queuedFuturesByKey.getOrDefault(key, List.of());
+            for (CompletableFuture<V> future : futures) {
+                if (!future.isDone()) {
+                    // we have a future that never came back for that key
+                    // but the publisher is done sending in data - it must be null
+                    // e.g. for key X when found no value
+                    future.complete(null);
+                }
+            }
+        }
+        valuesFuture.complete(values);
+    }
+
+    @Override
+    public synchronized void onError(Throwable ex) {
+        super.onError(ex);
+        ex = unwrapThrowable(ex);
+        // Complete the futures for the remaining keys with the exception.
+        for (int idx = 0; idx < queuedFutures.size(); idx++) {
+            K key = keys.get(idx);
+            List<CompletableFuture<V>> futures = queuedFuturesByKey.get(key);
+            if (!completedValuesByKey.containsKey(key)) {
+                for (CompletableFuture<V> future : futures) {
+                    future.completeExceptionally(ex);
+                }
+                // clear any cached view of this key because they all failed
+                helperIntegration.clearCacheView(key);
+            }
+        }
+        valuesFuture.completeExceptionally(ex);
+    }
+}
diff --git a/src/main/java/org/dataloader/reactive/ReactiveSupport.java b/src/main/java/org/dataloader/reactive/ReactiveSupport.java
new file mode 100644
index 0000000..fc03bb0
--- /dev/null
+++ b/src/main/java/org/dataloader/reactive/ReactiveSupport.java
@@ -0,0 +1,45 @@
+package org.dataloader.reactive;
+
+import org.dataloader.stats.StatisticsCollector;
+import org.reactivestreams.Subscriber;
+
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CompletableFuture;
+
+public class ReactiveSupport {
+
+    public static <K, V> Subscriber<V> batchSubscriber(
+            CompletableFuture<List<V>> valuesFuture,
+            List<K> keys,
+            List<Object> callContexts,
+            List<CompletableFuture<V>> queuedFutures,
+            ReactiveSupport.HelperIntegration<K> helperIntegration
+    ) {
+        return new BatchSubscriberImpl<>(valuesFuture, keys, callContexts, queuedFutures, helperIntegration);
+    }
+
+    public static <K, V> Subscriber<Map.Entry<K, V>> mappedBatchSubscriber(
+            CompletableFuture<List<V>> valuesFuture,
+            List<K> keys,
+            List<Object> callContexts,
+            List<CompletableFuture<V>> queuedFutures,
+            ReactiveSupport.HelperIntegration<K> helperIntegration
+    ) {
+        return new MappedBatchSubscriberImpl<>(valuesFuture, keys, callContexts, queuedFutures, helperIntegration);
+    }
+
+    /**
+     * Just some callbacks to the data loader code to do common tasks
+     *
+     * @param <K> for keys
+     */
+    public interface HelperIntegration<K> {
+
+        StatisticsCollector getStats();
+
+        void clearCacheView(K key);
+
+        void clearCacheEntriesOnExceptions(List<K> keys);
+    }
+}
diff --git a/src/main/java/org/dataloader/scheduler/BatchLoaderScheduler.java b/src/main/java/org/dataloader/scheduler/BatchLoaderScheduler.java
index 7cddd54..e7e95d9 100644
--- a/src/main/java/org/dataloader/scheduler/BatchLoaderScheduler.java
+++ b/src/main/java/org/dataloader/scheduler/BatchLoaderScheduler.java
@@ -5,6 +5,8 @@
 import org.dataloader.DataLoader;
 import org.dataloader.DataLoaderOptions;
 import org.dataloader.MappedBatchLoader;
+import org.dataloader.MappedBatchPublisher;
+import org.dataloader.BatchPublisher;
 
 import java.util.List;
 import java.util.Map;
@@ -42,6 +44,13 @@ interface ScheduledMappedBatchLoaderCall<K, V> {
         CompletionStage<Map<K, V>> invoke();
     }
 
+    /**
+     * This represents a callback that will invoke a {@link BatchPublisher} or {@link MappedBatchPublisher} function under the covers
+     */
+    interface ScheduledBatchPublisherCall {
+        void invoke();
+    }
+
     /**
      * This is called to schedule a {@link BatchLoader} call.
      *
@@ -71,4 +80,16 @@ interface ScheduledMappedBatchLoaderCall<K, V> {
      * @return a promise to the values that come from the {@link BatchLoader}
      */
     <K, V> CompletionStage<Map<K, V>> scheduleMappedBatchLoader(ScheduledMappedBatchLoaderCall<K, V> scheduledCall, List<K> keys, BatchLoaderEnvironment environment);
+
+    /**
+     * This is called to schedule a {@link BatchPublisher} call.
+     *
+     * @param scheduledCall the callback that needs to be invoked to allow the {@link BatchPublisher} to proceed.
+     * @param keys          this is the list of keys that will be passed to the {@link BatchPublisher}.
+     *                      This is provided only for informative reasons and, you can't change the keys that are used
+     * @param environment   this is the {@link BatchLoaderEnvironment} in place,
+     *                      which can be null if it's a simple {@link BatchPublisher} call
+     * @param <K>           the key type
+     */
+    <K> void scheduleBatchPublisher(ScheduledBatchPublisherCall scheduledCall, List<K> keys, BatchLoaderEnvironment environment);
 }
diff --git a/src/test/java/ReadmeExamples.java b/src/test/java/ReadmeExamples.java
index d25dfa7..9e30c90 100644
--- a/src/test/java/ReadmeExamples.java
+++ b/src/test/java/ReadmeExamples.java
@@ -1,11 +1,13 @@
 import org.dataloader.BatchLoader;
 import org.dataloader.BatchLoaderEnvironment;
 import org.dataloader.BatchLoaderWithContext;
+import org.dataloader.BatchPublisher;
 import org.dataloader.CacheMap;
 import org.dataloader.DataLoader;
 import org.dataloader.DataLoaderFactory;
 import org.dataloader.DataLoaderOptions;
 import org.dataloader.MappedBatchLoaderWithContext;
+import org.dataloader.MappedBatchPublisher;
 import org.dataloader.Try;
 import org.dataloader.fixtures.SecurityCtx;
 import org.dataloader.fixtures.User;
@@ -15,6 +17,8 @@
 import org.dataloader.scheduler.BatchLoaderScheduler;
 import org.dataloader.stats.Statistics;
 import org.dataloader.stats.ThreadLocalStatisticsCollector;
+import org.reactivestreams.Publisher;
+import org.reactivestreams.Subscriber;
 
 import java.time.Duration;
 import java.util.ArrayList;
@@ -171,7 +175,7 @@ private void tryExample() {
         }
     }
 
-    private void tryBatcLoader() {
+    private void tryBatchLoader() {
         DataLoader<String, User> dataLoader = DataLoaderFactory.newDataLoaderWithTry(new BatchLoader<String, Try<User>>() {
             @Override
             public CompletionStage<List<Try<User>>> load(List<String> keys) {
@@ -187,6 +191,28 @@ public CompletionStage<List<Try<User>>> load(List<String> keys) {
         });
     }
 
+    private void batchPublisher() {
+        BatchPublisher<Long, User> batchPublisher = new BatchPublisher<Long, User>() {
+            @Override
+            public void load(List<Long> userIds, Subscriber<User> userSubscriber) {
+                Publisher<User> userResults = userManager.streamUsersById(userIds);
+                userResults.subscribe(userSubscriber);
+            }
+        };
+        DataLoader<Long, User> userLoader = DataLoaderFactory.newPublisherDataLoader(batchPublisher);
+    }
+
+    private void mappedBatchPublisher() {
+        MappedBatchPublisher<Long, User> mappedBatchPublisher = new MappedBatchPublisher<Long, User>() {
+            @Override
+            public void load(Set<Long> userIds, Subscriber<Map.Entry<Long, User>> userEntrySubscriber) {
+                Publisher<Map.Entry<Long, User>> userEntries = userManager.streamUsersById(userIds);
+                userEntries.subscribe(userEntrySubscriber);
+            }
+        };
+        DataLoader<Long, User> userLoader = DataLoaderFactory.newMappedPublisherDataLoader(mappedBatchPublisher);
+    }
+
     DataLoader<String, User> userDataLoader;
 
     private void clearCacheOnError() {
@@ -304,6 +330,12 @@ public <K, V> CompletionStage<Map<K, V>> scheduleMappedBatchLoader(ScheduledMapp
                     return scheduledCall.invoke();
                 }).thenCompose(Function.identity());
             }
+
+            @Override
+            public <K> void scheduleBatchPublisher(ScheduledBatchPublisherCall scheduledCall, List<K> keys, BatchLoaderEnvironment environment) {
+                snooze(10);
+                scheduledCall.invoke();
+            }
         };
     }
 
diff --git a/src/test/java/org/dataloader/DataLoaderBatchLoaderEnvironmentTest.java b/src/test/java/org/dataloader/DataLoaderBatchLoaderEnvironmentTest.java
index 36e0ed4..90adbc5 100644
--- a/src/test/java/org/dataloader/DataLoaderBatchLoaderEnvironmentTest.java
+++ b/src/test/java/org/dataloader/DataLoaderBatchLoaderEnvironmentTest.java
@@ -1,11 +1,8 @@
 package org.dataloader;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.stream.Collectors;
@@ -14,8 +11,8 @@
 import static java.util.Collections.singletonList;
 import static org.dataloader.DataLoaderFactory.newDataLoader;
 import static org.dataloader.DataLoaderFactory.newMappedDataLoader;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertThat;
 
 /**
  * Tests related to context.  DataLoaderTest is getting to big and needs refactoring
@@ -50,10 +47,14 @@ public void context_is_passed_to_batch_loader_function() {
         loader.load("A");
         loader.load("B");
         loader.loadMany(asList("C", "D"));
+        Map<String, ?> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("E", null);
+        keysAndContexts.put("F", null);
+        loader.loadMany(keysAndContexts);
 
         List<String> results = loader.dispatchAndJoin();
 
-        assertThat(results, equalTo(asList("A-ctx", "B-ctx", "C-ctx", "D-ctx")));
+        assertThat(results, equalTo(asList("A-ctx", "B-ctx", "C-ctx", "D-ctx", "E-ctx", "F-ctx")));
     }
 
     @Test
@@ -66,10 +67,14 @@ public void key_contexts_are_passed_to_batch_loader_function() {
         loader.load("A", "aCtx");
         loader.load("B", "bCtx");
         loader.loadMany(asList("C", "D"), asList("cCtx", "dCtx"));
+        Map<String, String> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("E", "eCtx");
+        keysAndContexts.put("F", "fCtx");
+        loader.loadMany(keysAndContexts);
 
         List<String> results = loader.dispatchAndJoin();
 
-        assertThat(results, equalTo(asList("A-ctx-m:aCtx-l:aCtx", "B-ctx-m:bCtx-l:bCtx", "C-ctx-m:cCtx-l:cCtx", "D-ctx-m:dCtx-l:dCtx")));
+        assertThat(results, equalTo(asList("A-ctx-m:aCtx-l:aCtx", "B-ctx-m:bCtx-l:bCtx", "C-ctx-m:cCtx-l:cCtx", "D-ctx-m:dCtx-l:dCtx", "E-ctx-m:eCtx-l:eCtx", "F-ctx-m:fCtx-l:fCtx")));
     }
 
     @Test
@@ -82,12 +87,17 @@ public void key_contexts_are_passed_to_batch_loader_function_when_batching_disab
 
         CompletableFuture<String> aLoad = loader.load("A", "aCtx");
         CompletableFuture<String> bLoad = loader.load("B", "bCtx");
-        CompletableFuture<List<String>> canDLoad = loader.loadMany(asList("C", "D"), asList("cCtx", "dCtx"));
+        CompletableFuture<List<String>> cAndDLoad = loader.loadMany(asList("C", "D"), asList("cCtx", "dCtx"));
+        Map<String, String> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("E", "eCtx");
+        keysAndContexts.put("F", "fCtx");
+        CompletableFuture<Map<String, String>> eAndFLoad = loader.loadMany(keysAndContexts);
 
         List<String> results = new ArrayList<>(asList(aLoad.join(), bLoad.join()));
-        results.addAll(canDLoad.join());
+        results.addAll(cAndDLoad.join());
+        results.addAll(eAndFLoad.join().values());
 
-        assertThat(results, equalTo(asList("A-ctx-m:aCtx-l:aCtx", "B-ctx-m:bCtx-l:bCtx", "C-ctx-m:cCtx-l:cCtx", "D-ctx-m:dCtx-l:dCtx")));
+        assertThat(results, equalTo(asList("A-ctx-m:aCtx-l:aCtx", "B-ctx-m:bCtx-l:bCtx", "C-ctx-m:cCtx-l:cCtx", "D-ctx-m:dCtx-l:dCtx", "E-ctx-m:eCtx-l:eCtx", "F-ctx-m:fCtx-l:fCtx")));
     }
 
     @Test
@@ -101,9 +111,14 @@ public void missing_key_contexts_are_passed_to_batch_loader_function() {
         loader.load("B");
         loader.loadMany(asList("C", "D"), singletonList("cCtx"));
 
+        Map<String, String> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("E", "eCtx");
+        keysAndContexts.put("F", null);
+        loader.loadMany(keysAndContexts);
+
         List<String> results = loader.dispatchAndJoin();
 
-        assertThat(results, equalTo(asList("A-ctx-m:aCtx-l:aCtx", "B-ctx-m:null-l:null", "C-ctx-m:cCtx-l:cCtx", "D-ctx-m:null-l:null")));
+        assertThat(results, equalTo(asList("A-ctx-m:aCtx-l:aCtx", "B-ctx-m:null-l:null", "C-ctx-m:cCtx-l:cCtx", "D-ctx-m:null-l:null", "E-ctx-m:eCtx-l:eCtx", "F-ctx-m:null-l:null")));
     }
 
     @Test
@@ -125,9 +140,14 @@ public void context_is_passed_to_map_batch_loader_function() {
         loader.load("B");
         loader.loadMany(asList("C", "D"), singletonList("cCtx"));
 
+        Map<String, String> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("E", "eCtx");
+        keysAndContexts.put("F", null);
+        loader.loadMany(keysAndContexts);
+
         List<String> results = loader.dispatchAndJoin();
 
-        assertThat(results, equalTo(asList("A-ctx-aCtx", "B-ctx-null", "C-ctx-cCtx", "D-ctx-null")));
+        assertThat(results, equalTo(asList("A-ctx-aCtx", "B-ctx-null", "C-ctx-cCtx", "D-ctx-null", "E-ctx-eCtx", "F-ctx-null")));
     }
 
     @Test
@@ -142,9 +162,14 @@ public void null_is_passed_as_context_if_you_do_nothing() {
         loader.load("B");
         loader.loadMany(asList("C", "D"));
 
+        Map<String, String> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("E", null);
+        keysAndContexts.put("F", null);
+        loader.loadMany(keysAndContexts);
+
         List<String> results = loader.dispatchAndJoin();
 
-        assertThat(results, equalTo(asList("A-null", "B-null", "C-null", "D-null")));
+        assertThat(results, equalTo(asList("A-null", "B-null", "C-null", "D-null", "E-null", "F-null")));
     }
 
     @Test
@@ -160,9 +185,14 @@ public void null_is_passed_as_context_to_map_loader_if_you_do_nothing() {
         loader.load("B");
         loader.loadMany(asList("C", "D"));
 
+        Map<String, String> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("E", null);
+        keysAndContexts.put("F", null);
+        loader.loadMany(keysAndContexts);
+
         List<String> results = loader.dispatchAndJoin();
 
-        assertThat(results, equalTo(asList("A-null", "B-null", "C-null", "D-null")));
+        assertThat(results, equalTo(asList("A-null", "B-null", "C-null", "D-null", "E-null", "F-null")));
     }
 
     @Test
diff --git a/src/test/java/org/dataloader/DataLoaderCacheMapTest.java b/src/test/java/org/dataloader/DataLoaderCacheMapTest.java
index abfc8d3..a7b82b7 100644
--- a/src/test/java/org/dataloader/DataLoaderCacheMapTest.java
+++ b/src/test/java/org/dataloader/DataLoaderCacheMapTest.java
@@ -1,6 +1,6 @@
 package org.dataloader;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -8,8 +8,8 @@
 import java.util.concurrent.CompletableFuture;
 
 import static org.dataloader.DataLoaderFactory.newDataLoader;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertThat;
 
 /**
  * Tests for cacheMap functionality..
diff --git a/src/test/java/org/dataloader/DataLoaderIfPresentTest.java b/src/test/java/org/dataloader/DataLoaderIfPresentTest.java
index 1d897f2..f0a50d6 100644
--- a/src/test/java/org/dataloader/DataLoaderIfPresentTest.java
+++ b/src/test/java/org/dataloader/DataLoaderIfPresentTest.java
@@ -1,15 +1,15 @@
 package org.dataloader;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
 
 import static org.dataloader.DataLoaderFactory.newDataLoader;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.sameInstance;
-import static org.junit.Assert.assertThat;
 
 /**
  * Tests for IfPresent and IfCompleted functionality.
diff --git a/src/test/java/org/dataloader/DataLoaderMapBatchLoaderTest.java b/src/test/java/org/dataloader/DataLoaderMapBatchLoaderTest.java
deleted file mode 100644
index 0fced79..0000000
--- a/src/test/java/org/dataloader/DataLoaderMapBatchLoaderTest.java
+++ /dev/null
@@ -1,184 +0,0 @@
-package org.dataloader;
-
-import org.junit.Test;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.atomic.AtomicInteger;
-
-import static java.util.Arrays.asList;
-import static java.util.Collections.singletonList;
-import static org.awaitility.Awaitility.await;
-import static org.dataloader.DataLoaderFactory.newDataLoader;
-import static org.dataloader.DataLoaderOptions.newOptions;
-import static org.dataloader.fixtures.TestKit.futureError;
-import static org.dataloader.fixtures.TestKit.listFrom;
-import static org.dataloader.impl.CompletableFutureKit.cause;
-import static org.hamcrest.Matchers.equalTo;
-import static org.hamcrest.Matchers.instanceOf;
-import static org.hamcrest.Matchers.is;
-import static org.junit.Assert.assertThat;
-
-/**
- * Much of the tests that related to {@link MappedBatchLoader} also related to
- * {@link org.dataloader.BatchLoader}.  This is white box testing somewhat because we could have repeated
- * ALL the tests in {@link org.dataloader.DataLoaderTest} here as well but chose not to because we KNOW that
- * DataLoader differs only a little in how it handles the 2 types of loader functions. We choose to grab some
- * common functionality for repeat testing and otherwise rely on the very complete other tests.
- */
-public class DataLoaderMapBatchLoaderTest {
-
-    MappedBatchLoader<String, String> evensOnlyMappedBatchLoader = (keys) -> {
-        Map<String, String> mapOfResults = new HashMap<>();
-
-        AtomicInteger index = new AtomicInteger();
-        keys.forEach(k -> {
-            int i = index.getAndIncrement();
-            if (i % 2 == 0) {
-                mapOfResults.put(k, k);
-            }
-        });
-        return CompletableFuture.completedFuture(mapOfResults);
-    };
-
-    private static <K, V> DataLoader<K, V> idMapLoader(DataLoaderOptions options, List<Collection<K>> loadCalls) {
-        MappedBatchLoader<K, V> kvBatchLoader = (keys) -> {
-            loadCalls.add(new ArrayList<>(keys));
-            Map<K, V> map = new HashMap<>();
-            //noinspection unchecked
-            keys.forEach(k -> map.put(k, (V) k));
-            return CompletableFuture.completedFuture(map);
-        };
-        return DataLoaderFactory.newMappedDataLoader(kvBatchLoader, options);
-    }
-
-    private static <K, V> DataLoader<K, V> idMapLoaderBlowsUps(
-            DataLoaderOptions options, List<Collection<K>> loadCalls) {
-        return newDataLoader((keys) -> {
-            loadCalls.add(new ArrayList<>(keys));
-            return futureError();
-        }, options);
-    }
-
-
-    @Test
-    public void basic_map_batch_loading() {
-        DataLoader<String, String> loader = DataLoaderFactory.newMappedDataLoader(evensOnlyMappedBatchLoader);
-
-        loader.load("A");
-        loader.load("B");
-        loader.loadMany(asList("C", "D"));
-
-        List<String> results = loader.dispatchAndJoin();
-
-        assertThat(results.size(), equalTo(4));
-        assertThat(results, equalTo(asList("A", null, "C", null)));
-    }
-
-
-    @Test
-    public void should_map_Batch_multiple_requests() throws ExecutionException, InterruptedException {
-        List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> identityLoader = idMapLoader(new DataLoaderOptions(), loadCalls);
-
-        CompletableFuture<Integer> future1 = identityLoader.load(1);
-        CompletableFuture<Integer> future2 = identityLoader.load(2);
-        identityLoader.dispatch();
-
-        await().until(() -> future1.isDone() && future2.isDone());
-        assertThat(future1.get(), equalTo(1));
-        assertThat(future2.get(), equalTo(2));
-        assertThat(loadCalls, equalTo(singletonList(asList(1, 2))));
-    }
-
-    @Test
-    public void can_split_max_batch_sizes_correctly() {
-        List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> identityLoader = idMapLoader(newOptions().setMaxBatchSize(5), loadCalls);
-
-        for (int i = 0; i < 21; i++) {
-            identityLoader.load(i);
-        }
-        List<Collection<Integer>> expectedCalls = new ArrayList<>();
-        expectedCalls.add(listFrom(0, 5));
-        expectedCalls.add(listFrom(5, 10));
-        expectedCalls.add(listFrom(10, 15));
-        expectedCalls.add(listFrom(15, 20));
-        expectedCalls.add(listFrom(20, 21));
-
-        List<Integer> result = identityLoader.dispatch().join();
-
-        assertThat(result, equalTo(listFrom(0, 21)));
-        assertThat(loadCalls, equalTo(expectedCalls));
-    }
-
-    @Test
-    public void should_Propagate_error_to_all_loads() {
-        List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> errorLoader = idMapLoaderBlowsUps(new DataLoaderOptions(), loadCalls);
-
-        CompletableFuture<Integer> future1 = errorLoader.load(1);
-        CompletableFuture<Integer> future2 = errorLoader.load(2);
-        errorLoader.dispatch();
-
-        await().until(future1::isDone);
-
-        assertThat(future1.isCompletedExceptionally(), is(true));
-        Throwable cause = cause(future1);
-        assert cause != null;
-        assertThat(cause, instanceOf(IllegalStateException.class));
-        assertThat(cause.getMessage(), equalTo("Error"));
-
-        await().until(future2::isDone);
-        cause = cause(future2);
-        assert cause != null;
-        assertThat(cause.getMessage(), equalTo(cause.getMessage()));
-
-        assertThat(loadCalls, equalTo(singletonList(asList(1, 2))));
-    }
-
-    @Test
-    public void should_work_with_duplicate_keys_when_caching_disabled() throws ExecutionException, InterruptedException {
-        List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader =
-                idMapLoader(newOptions().setCachingEnabled(false), loadCalls);
-
-        CompletableFuture<String> future1 = identityLoader.load("A");
-        CompletableFuture<String> future2 = identityLoader.load("B");
-        CompletableFuture<String> future3 = identityLoader.load("A");
-        identityLoader.dispatch();
-
-        await().until(() -> future1.isDone() && future2.isDone() && future3.isDone());
-        assertThat(future1.get(), equalTo("A"));
-        assertThat(future2.get(), equalTo("B"));
-        assertThat(future3.get(), equalTo("A"));
-
-        // the map batch functions use a set of keys as input and hence remove duplicates unlike list variant
-        assertThat(loadCalls, equalTo(singletonList(asList("A", "B"))));
-    }
-
-    @Test
-    public void should_work_with_duplicate_keys_when_caching_enabled() throws ExecutionException, InterruptedException {
-        List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader =
-                idMapLoader(newOptions().setCachingEnabled(true), loadCalls);
-
-        CompletableFuture<String> future1 = identityLoader.load("A");
-        CompletableFuture<String> future2 = identityLoader.load("B");
-        CompletableFuture<String> future3 = identityLoader.load("A");
-        identityLoader.dispatch();
-
-        await().until(() -> future1.isDone() && future2.isDone() && future3.isDone());
-        assertThat(future1.get(), equalTo("A"));
-        assertThat(future2.get(), equalTo("B"));
-        assertThat(future3.get(), equalTo("A"));
-        assertThat(loadCalls, equalTo(singletonList(asList("A", "B"))));
-    }
-
-
-}
diff --git a/src/test/java/org/dataloader/DataLoaderRegistryTest.java b/src/test/java/org/dataloader/DataLoaderRegistryTest.java
index aeaf668..bd1534d 100644
--- a/src/test/java/org/dataloader/DataLoaderRegistryTest.java
+++ b/src/test/java/org/dataloader/DataLoaderRegistryTest.java
@@ -2,16 +2,16 @@
 
 import org.dataloader.stats.SimpleStatisticsCollector;
 import org.dataloader.stats.Statistics;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.concurrent.CompletableFuture;
 
 import static java.util.Arrays.asList;
 import static org.dataloader.DataLoaderFactory.newDataLoader;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasItems;
 import static org.hamcrest.Matchers.sameInstance;
-import static org.junit.Assert.assertThat;
 
 public class DataLoaderRegistryTest {
     final BatchLoader<Object, Object> identityBatchLoader = CompletableFuture::completedFuture;
diff --git a/src/test/java/org/dataloader/DataLoaderStatsTest.java b/src/test/java/org/dataloader/DataLoaderStatsTest.java
index c2faa50..b8393e6 100644
--- a/src/test/java/org/dataloader/DataLoaderStatsTest.java
+++ b/src/test/java/org/dataloader/DataLoaderStatsTest.java
@@ -9,19 +9,20 @@
 import org.dataloader.stats.context.IncrementCacheHitCountStatisticsContext;
 import org.dataloader.stats.context.IncrementLoadCountStatisticsContext;
 import org.dataloader.stats.context.IncrementLoadErrorCountStatisticsContext;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 
 import static java.util.Arrays.asList;
 import static java.util.Collections.singletonList;
 import static java.util.concurrent.CompletableFuture.completedFuture;
 import static org.dataloader.DataLoaderFactory.newDataLoader;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasSize;
-import static org.junit.Assert.assertThat;
 
 /**
  * Tests related to stats.  DataLoaderTest is getting to big and needs refactoring
@@ -118,9 +119,10 @@ public void stats_are_collected_with_caching_disabled() {
         loader.load("A");
         loader.load("B");
         loader.loadMany(asList("C", "D"));
+        loader.loadMany(Map.of("E", "E", "F", "F"));
 
         Statistics stats = loader.getStatistics();
-        assertThat(stats.getLoadCount(), equalTo(4L));
+        assertThat(stats.getLoadCount(), equalTo(6L));
         assertThat(stats.getBatchInvokeCount(), equalTo(0L));
         assertThat(stats.getBatchLoadCount(), equalTo(0L));
         assertThat(stats.getCacheHitCount(), equalTo(0L));
@@ -128,9 +130,9 @@ public void stats_are_collected_with_caching_disabled() {
         loader.dispatch();
 
         stats = loader.getStatistics();
-        assertThat(stats.getLoadCount(), equalTo(4L));
+        assertThat(stats.getLoadCount(), equalTo(6L));
         assertThat(stats.getBatchInvokeCount(), equalTo(1L));
-        assertThat(stats.getBatchLoadCount(), equalTo(4L));
+        assertThat(stats.getBatchLoadCount(), equalTo(6L));
         assertThat(stats.getCacheHitCount(), equalTo(0L));
 
         loader.load("A");
@@ -139,9 +141,9 @@ public void stats_are_collected_with_caching_disabled() {
         loader.dispatch();
 
         stats = loader.getStatistics();
-        assertThat(stats.getLoadCount(), equalTo(6L));
+        assertThat(stats.getLoadCount(), equalTo(8L));
         assertThat(stats.getBatchInvokeCount(), equalTo(2L));
-        assertThat(stats.getBatchLoadCount(), equalTo(6L));
+        assertThat(stats.getBatchLoadCount(), equalTo(8L));
         assertThat(stats.getCacheHitCount(), equalTo(0L));
     }
 
diff --git a/src/test/java/org/dataloader/DataLoaderTest.java b/src/test/java/org/dataloader/DataLoaderTest.java
index 18dd6f8..c4ae883 100644
--- a/src/test/java/org/dataloader/DataLoaderTest.java
+++ b/src/test/java/org/dataloader/DataLoaderTest.java
@@ -16,38 +16,54 @@
 
 package org.dataloader;
 
+import org.awaitility.Duration;
 import org.dataloader.fixtures.CustomCacheMap;
 import org.dataloader.fixtures.JsonObject;
-import org.dataloader.fixtures.TestKit;
 import org.dataloader.fixtures.User;
 import org.dataloader.fixtures.UserManager;
+import org.dataloader.fixtures.parameterized.ListDataLoaderFactory;
+import org.dataloader.fixtures.parameterized.MappedDataLoaderFactory;
+import org.dataloader.fixtures.parameterized.MappedPublisherDataLoaderFactory;
+import org.dataloader.fixtures.parameterized.PublisherDataLoaderFactory;
+import org.dataloader.fixtures.parameterized.TestDataLoaderFactory;
+import org.dataloader.fixtures.parameterized.TestReactiveDataLoaderFactory;
 import org.dataloader.impl.CompletableFutureKit;
-import org.junit.Test;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.List;
+import org.dataloader.impl.DataLoaderAssertionException;
+import org.junit.jupiter.api.Named;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.util.*;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Function;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import static java.util.Arrays.asList;
-import static java.util.Collections.emptyList;
-import static java.util.Collections.singletonList;
+import static java.util.Collections.*;
+import static java.util.concurrent.CompletableFuture.*;
 import static org.awaitility.Awaitility.await;
 import static org.dataloader.DataLoaderFactory.newDataLoader;
+import static org.dataloader.DataLoaderFactory.newMappedDataLoader;
+import static org.dataloader.DataLoaderFactory.newMappedPublisherDataLoader;
+import static org.dataloader.DataLoaderFactory.newMappedPublisherDataLoaderWithTry;
+import static org.dataloader.DataLoaderFactory.newPublisherDataLoader;
+import static org.dataloader.DataLoaderFactory.newPublisherDataLoaderWithTry;
 import static org.dataloader.DataLoaderOptions.newOptions;
+import static org.dataloader.fixtures.TestKit.areAllDone;
 import static org.dataloader.fixtures.TestKit.listFrom;
 import static org.dataloader.impl.CompletableFutureKit.cause;
-import static org.hamcrest.Matchers.empty;
-import static org.hamcrest.Matchers.equalTo;
-import static org.hamcrest.Matchers.instanceOf;
-import static org.hamcrest.Matchers.is;
-import static org.junit.Assert.assertArrayEquals;
-import static org.junit.Assert.assertThat;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.*;
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.fail;
 
 /**
  * Tests for {@link DataLoader}.
@@ -64,7 +80,7 @@ public class DataLoaderTest {
     @Test
     public void should_Build_a_really_really_simple_data_loader() {
         AtomicBoolean success = new AtomicBoolean();
-        DataLoader<Integer, Integer> identityLoader = newDataLoader(keysAsValues());
+        DataLoader<Integer, Integer> identityLoader = newDataLoader(CompletableFuture::completedFuture);
 
         CompletionStage<Integer> future1 = identityLoader.load(1);
 
@@ -77,9 +93,42 @@ public void should_Build_a_really_really_simple_data_loader() {
     }
 
     @Test
-    public void should_Support_loading_multiple_keys_in_one_call() {
+    public void basic_map_batch_loading() {
+        MappedBatchLoader<String, String> evensOnlyMappedBatchLoader = (keys) -> {
+            Map<String, String> mapOfResults = new HashMap<>();
+
+            AtomicInteger index = new AtomicInteger();
+            keys.forEach(k -> {
+                int i = index.getAndIncrement();
+                if (i % 2 == 0) {
+                    mapOfResults.put(k, k);
+                }
+            });
+            return completedFuture(mapOfResults);
+        };
+        DataLoader<String, String> loader = DataLoaderFactory.newMappedDataLoader(evensOnlyMappedBatchLoader);
+
+        final List<String> keys = asList("C", "D");
+        final Map<String, ?> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("E", null);
+        keysAndContexts.put("F", null);
+
+        loader.load("A");
+        loader.load("B");
+        loader.loadMany(keys);
+        loader.loadMany(keysAndContexts);
+
+        List<String> results = loader.dispatchAndJoin();
+
+        assertThat(results.size(), equalTo(6));
+        assertThat(results, equalTo(asList("A", null, "C", null, "E", null)));
+    }
+
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Support_loading_multiple_keys_in_one_call_via_list(TestDataLoaderFactory factory) {
         AtomicBoolean success = new AtomicBoolean();
-        DataLoader<Integer, Integer> identityLoader = newDataLoader(keysAsValues());
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), new ArrayList<>());
 
         CompletionStage<List<Integer>> futureAll = identityLoader.loadMany(asList(1, 2));
         futureAll.thenAccept(promisedValues -> {
@@ -91,10 +140,31 @@ public void should_Support_loading_multiple_keys_in_one_call() {
         assertThat(futureAll.toCompletableFuture().join(), equalTo(asList(1, 2)));
     }
 
-    @Test
-    public void should_Resolve_to_empty_list_when_no_keys_supplied() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Support_loading_multiple_keys_in_one_call_via_map(TestDataLoaderFactory factory) {
+        AtomicBoolean success = new AtomicBoolean();
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), new ArrayList<>());
+
+        final Map<Integer, ?> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put(1, null);
+        keysAndContexts.put(2, null);
+
+        CompletionStage<Map<Integer, Integer>> futureAll = identityLoader.loadMany(keysAndContexts);
+        futureAll.thenAccept(promisedValues -> {
+            assertThat(promisedValues.size(), is(2));
+            success.set(true);
+        });
+        identityLoader.dispatch();
+        await().untilAtomic(success, is(true));
+        assertThat(futureAll.toCompletableFuture().join(), equalTo(Map.of(1, 1, 2, 2)));
+    }
+
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Resolve_to_empty_list_when_no_keys_supplied(TestDataLoaderFactory factory) {
         AtomicBoolean success = new AtomicBoolean();
-        DataLoader<Integer, Integer> identityLoader = newDataLoader(keysAsValues());
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), new ArrayList<>());
         CompletableFuture<List<Integer>> futureEmpty = identityLoader.loadMany(emptyList());
         futureEmpty.thenAccept(promisedValues -> {
             assertThat(promisedValues.size(), is(0));
@@ -105,10 +175,26 @@ public void should_Resolve_to_empty_list_when_no_keys_supplied() {
         assertThat(futureEmpty.join(), empty());
     }
 
-    @Test
-    public void should_Return_zero_entries_dispatched_when_no_keys_supplied() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Resolve_to_empty_map_when_no_keys_supplied(TestDataLoaderFactory factory) {
+        AtomicBoolean success = new AtomicBoolean();
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), new ArrayList<>());
+        CompletableFuture<Map<Integer, Integer>> futureEmpty = identityLoader.loadMany(emptyMap());
+        futureEmpty.thenAccept(promisedValues -> {
+            assertThat(promisedValues.size(), is(0));
+            success.set(true);
+        });
+        identityLoader.dispatch();
+        await().untilAtomic(success, is(true));
+        assertThat(futureEmpty.join(), anEmptyMap());
+    }
+
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Return_zero_entries_dispatched_when_no_keys_supplied_via_list(TestDataLoaderFactory factory) {
         AtomicBoolean success = new AtomicBoolean();
-        DataLoader<Integer, Integer> identityLoader = newDataLoader(keysAsValues());
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), new ArrayList<>());
         CompletableFuture<List<Integer>> futureEmpty = identityLoader.loadMany(emptyList());
         futureEmpty.thenAccept(promisedValues -> {
             assertThat(promisedValues.size(), is(0));
@@ -119,10 +205,26 @@ public void should_Return_zero_entries_dispatched_when_no_keys_supplied() {
         assertThat(dispatchResult.getKeysCount(), equalTo(0));
     }
 
-    @Test
-    public void should_Batch_multiple_requests() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Return_zero_entries_dispatched_when_no_keys_supplied_via_map(TestDataLoaderFactory factory) {
+        AtomicBoolean success = new AtomicBoolean();
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), new ArrayList<>());
+        CompletableFuture<Map<Integer, Integer>> futureEmpty = identityLoader.loadMany(emptyMap());
+        futureEmpty.thenAccept(promisedValues -> {
+            assertThat(promisedValues.size(), is(0));
+            success.set(true);
+        });
+        DispatchResult<Integer> dispatchResult = identityLoader.dispatchWithCounts();
+        await().untilAtomic(success, is(true));
+        assertThat(dispatchResult.getKeysCount(), equalTo(0));
+    }
+
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Batch_multiple_requests(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Integer> future1 = identityLoader.load(1);
         CompletableFuture<Integer> future2 = identityLoader.load(2);
@@ -134,10 +236,11 @@ public void should_Batch_multiple_requests() throws ExecutionException, Interrup
         assertThat(loadCalls, equalTo(singletonList(asList(1, 2))));
     }
 
-    @Test
-    public void should_Return_number_of_batched_entries() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Return_number_of_batched_entries(TestDataLoaderFactory factory) {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Integer> future1 = identityLoader.load(1);
         CompletableFuture<Integer> future2 = identityLoader.load(2);
@@ -148,10 +251,11 @@ public void should_Return_number_of_batched_entries() {
         assertThat(dispatchResult.getPromisedResults().isDone(), equalTo(true));
     }
 
-    @Test
-    public void should_Coalesce_identical_requests() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Coalesce_identical_requests(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Integer> future1a = identityLoader.load(1);
         CompletableFuture<Integer> future1b = identityLoader.load(1);
@@ -164,10 +268,11 @@ public void should_Coalesce_identical_requests() throws ExecutionException, Inte
         assertThat(loadCalls, equalTo(singletonList(singletonList(1))));
     }
 
-    @Test
-    public void should_Cache_repeated_requests() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Cache_repeated_requests(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<String> future1 = identityLoader.load("A");
         CompletableFuture<String> future2 = identityLoader.load("B");
@@ -199,10 +304,11 @@ public void should_Cache_repeated_requests() throws ExecutionException, Interrup
         assertThat(loadCalls, equalTo(asList(asList("A", "B"), singletonList("C"))));
     }
 
-    @Test
-    public void should_Not_redispatch_previous_load() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Not_redispatch_previous_load(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<String> future1 = identityLoader.load("A");
         identityLoader.dispatch();
@@ -216,10 +322,11 @@ public void should_Not_redispatch_previous_load() throws ExecutionException, Int
         assertThat(loadCalls, equalTo(asList(singletonList("A"), singletonList("B"))));
     }
 
-    @Test
-    public void should_Cache_on_redispatch() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Cache_on_redispatch(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<String> future1 = identityLoader.load("A");
         identityLoader.dispatch();
@@ -227,16 +334,24 @@ public void should_Cache_on_redispatch() throws ExecutionException, InterruptedE
         CompletableFuture<List<String>> future2 = identityLoader.loadMany(asList("A", "B"));
         identityLoader.dispatch();
 
-        await().until(() -> future1.isDone() && future2.isDone());
+        Map<String, ?> keysAndContexts = new LinkedHashMap<>();
+        keysAndContexts.put("A", null);
+        keysAndContexts.put("C", null);
+        CompletableFuture<Map<String, String>> future3 = identityLoader.loadMany(keysAndContexts);
+        identityLoader.dispatch();
+
+        await().until(() -> future1.isDone() && future2.isDone() && future3.isDone());
         assertThat(future1.get(), equalTo("A"));
         assertThat(future2.get(), equalTo(asList("A", "B")));
-        assertThat(loadCalls, equalTo(asList(singletonList("A"), singletonList("B"))));
+        assertThat(future3.get(), equalTo(keysAndContexts.entrySet().stream().collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getKey))));
+        assertThat(loadCalls, equalTo(asList(singletonList("A"), singletonList("B"), singletonList("C"))));
     }
 
-    @Test
-    public void should_Clear_single_value_in_loader() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Clear_single_value_in_loader(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<String> future1 = identityLoader.load("A");
         CompletableFuture<String> future2 = identityLoader.load("B");
@@ -261,10 +376,11 @@ public void should_Clear_single_value_in_loader() throws ExecutionException, Int
         assertThat(loadCalls, equalTo(asList(asList("A", "B"), singletonList("A"))));
     }
 
-    @Test
-    public void should_Clear_all_values_in_loader() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Clear_all_values_in_loader(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<String> future1 = identityLoader.load("A");
         CompletableFuture<String> future2 = identityLoader.load("B");
@@ -288,10 +404,11 @@ public void should_Clear_all_values_in_loader() throws ExecutionException, Inter
         assertThat(loadCalls, equalTo(asList(asList("A", "B"), asList("A", "B"))));
     }
 
-    @Test
-    public void should_Allow_priming_the_cache() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Allow_priming_the_cache(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         DataLoader<String, String> dlFluency = identityLoader.prime("A", "A");
         assertThat(dlFluency, equalTo(identityLoader));
@@ -306,10 +423,11 @@ public void should_Allow_priming_the_cache() throws ExecutionException, Interrup
         assertThat(loadCalls, equalTo(singletonList(singletonList("B"))));
     }
 
-    @Test
-    public void should_Not_prime_keys_that_already_exist() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Not_prime_keys_that_already_exist(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         identityLoader.prime("A", "X");
 
@@ -334,10 +452,11 @@ public void should_Not_prime_keys_that_already_exist() throws ExecutionException
         assertThat(loadCalls, equalTo(singletonList(singletonList("B"))));
     }
 
-    @Test
-    public void should_Allow_to_forcefully_prime_the_cache() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Allow_to_forcefully_prime_the_cache(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         identityLoader.prime("A", "X");
 
@@ -362,12 +481,13 @@ public void should_Allow_to_forcefully_prime_the_cache() throws ExecutionExcepti
         assertThat(loadCalls, equalTo(singletonList(singletonList("B"))));
     }
 
-    @Test
-    public void should_Allow_priming_the_cache_with_a_future() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Allow_priming_the_cache_with_a_future(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
-        DataLoader<String, String> dlFluency = identityLoader.prime("A", CompletableFuture.completedFuture("A"));
+        DataLoader<String, String> dlFluency = identityLoader.prime("A", completedFuture("A"));
         assertThat(dlFluency, equalTo(identityLoader));
 
         CompletableFuture<String> future1 = identityLoader.load("A");
@@ -380,10 +500,11 @@ public void should_Allow_priming_the_cache_with_a_future() throws ExecutionExcep
         assertThat(loadCalls, equalTo(singletonList(singletonList("B"))));
     }
 
-    @Test
-    public void should_not_Cache_failed_fetches_on_complete_failure() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_not_Cache_failed_fetches_on_complete_failure(TestDataLoaderFactory factory) {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> errorLoader = idLoaderBlowsUps(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Integer> errorLoader = factory.idLoaderBlowsUps(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Integer> future1 = errorLoader.load(1);
         errorLoader.dispatch();
@@ -401,10 +522,11 @@ public void should_not_Cache_failed_fetches_on_complete_failure() {
         assertThat(loadCalls, equalTo(asList(singletonList(1), singletonList(1))));
     }
 
-    @Test
-    public void should_Resolve_to_error_to_indicate_failure() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Resolve_to_error_to_indicate_failure(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Object> evenLoader = idLoaderOddEvenExceptions(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Object> evenLoader = factory.idLoaderOddEvenExceptions(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Object> future1 = evenLoader.load(1);
         evenLoader.dispatch();
@@ -423,11 +545,12 @@ public void should_Resolve_to_error_to_indicate_failure() throws ExecutionExcept
 
     // Accept any kind of key.
 
-    @Test
-    public void should_Represent_failures_and_successes_simultaneously() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Represent_failures_and_successes_simultaneously(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         AtomicBoolean success = new AtomicBoolean();
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Object> evenLoader = idLoaderOddEvenExceptions(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Object> evenLoader = factory.idLoaderOddEvenExceptions(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Object> future1 = evenLoader.load(1);
         CompletableFuture<Object> future2 = evenLoader.load(2);
@@ -449,10 +572,11 @@ public void should_Represent_failures_and_successes_simultaneously() throws Exec
 
     // Accepts options
 
-    @Test
-    public void should_Cache_failed_fetches() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Cache_failed_fetches(TestDataLoaderFactory factory) {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Object> errorLoader = idLoaderAllExceptions(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Object> errorLoader = factory.idLoaderAllExceptions(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Object> future1 = errorLoader.load(1);
         errorLoader.dispatch();
@@ -471,11 +595,12 @@ public void should_Cache_failed_fetches() {
         assertThat(loadCalls, equalTo(singletonList(singletonList(1))));
     }
 
-    @Test
-    public void should_NOT_Cache_failed_fetches_if_told_not_too() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_NOT_Cache_failed_fetches_if_told_not_too(TestDataLoaderFactory factory) {
         DataLoaderOptions options = DataLoaderOptions.newOptions().setCachingExceptionsEnabled(false);
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Object> errorLoader = idLoaderAllExceptions(options, loadCalls);
+        DataLoader<Integer, Object> errorLoader = factory.idLoaderAllExceptions(options, loadCalls);
 
         CompletableFuture<Object> future1 = errorLoader.load(1);
         errorLoader.dispatch();
@@ -497,10 +622,11 @@ public void should_NOT_Cache_failed_fetches_if_told_not_too() {
 
     // Accepts object key in custom cacheKey function
 
-    @Test
-    public void should_Handle_priming_the_cache_with_an_error() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Handle_priming_the_cache_with_an_error(TestDataLoaderFactory factory) {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         identityLoader.prime(1, new IllegalStateException("Error"));
 
@@ -513,10 +639,11 @@ public void should_Handle_priming_the_cache_with_an_error() {
         assertThat(loadCalls, equalTo(emptyList()));
     }
 
-    @Test
-    public void should_Clear_values_from_cache_after_errors() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Clear_values_from_cache_after_errors(TestDataLoaderFactory factory) {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> errorLoader = idLoaderBlowsUps(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Integer> errorLoader = factory.idLoaderBlowsUps(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Integer> future1 = errorLoader.load(1);
         future1.handle((value, t) -> {
@@ -548,10 +675,11 @@ public void should_Clear_values_from_cache_after_errors() {
         assertThat(loadCalls, equalTo(asList(singletonList(1), singletonList(1))));
     }
 
-    @Test
-    public void should_Propagate_error_to_all_loads() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Propagate_error_to_all_loads(TestDataLoaderFactory factory) {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> errorLoader = idLoaderBlowsUps(new DataLoaderOptions(), loadCalls);
+        DataLoader<Integer, Integer> errorLoader = factory.idLoaderBlowsUps(new DataLoaderOptions(), loadCalls);
 
         CompletableFuture<Integer> future1 = errorLoader.load(1);
         CompletableFuture<Integer> future2 = errorLoader.load(2);
@@ -571,10 +699,11 @@ public void should_Propagate_error_to_all_loads() {
         assertThat(loadCalls, equalTo(singletonList(asList(1, 2))));
     }
 
-    @Test
-    public void should_Accept_objects_as_keys() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Accept_objects_as_keys(TestDataLoaderFactory factory) {
         List<Collection<Object>> loadCalls = new ArrayList<>();
-        DataLoader<Object, Object> identityLoader = idLoader(new DataLoaderOptions(), loadCalls);
+        DataLoader<Object, Object> identityLoader = factory.idLoader(new DataLoaderOptions(), loadCalls);
 
         Object keyA = new Object();
         Object keyB = new Object();
@@ -612,11 +741,12 @@ public void should_Accept_objects_as_keys() {
         assertThat(loadCalls.get(1).toArray()[0], equalTo(keyA));
     }
 
-    @Test
-    public void should_Disable_caching() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Disable_caching(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
         DataLoader<String, String> identityLoader =
-                idLoader(newOptions().setCachingEnabled(false), loadCalls);
+                factory.idLoader(newOptions().setCachingEnabled(false), loadCalls);
 
         CompletableFuture<String> future1 = identityLoader.load("A");
         CompletableFuture<String> future2 = identityLoader.load("B");
@@ -649,11 +779,12 @@ public void should_Disable_caching() throws ExecutionException, InterruptedExcep
                 asList("A", "C"), asList("A", "B", "C"))));
     }
 
-    @Test
-    public void should_work_with_duplicate_keys_when_caching_disabled() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_work_with_duplicate_keys_when_caching_disabled(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
         DataLoader<String, String> identityLoader =
-                idLoader(newOptions().setCachingEnabled(false), loadCalls);
+                factory.idLoader(newOptions().setCachingEnabled(false), loadCalls);
 
         CompletableFuture<String> future1 = identityLoader.load("A");
         CompletableFuture<String> future2 = identityLoader.load("B");
@@ -664,14 +795,19 @@ public void should_work_with_duplicate_keys_when_caching_disabled() throws Execu
         assertThat(future1.get(), equalTo("A"));
         assertThat(future2.get(), equalTo("B"));
         assertThat(future3.get(), equalTo("A"));
-        assertThat(loadCalls, equalTo(singletonList(asList("A", "B", "A"))));
+        if (factory instanceof MappedDataLoaderFactory || factory instanceof MappedPublisherDataLoaderFactory) {
+            assertThat(loadCalls, equalTo(singletonList(asList("A", "B"))));
+        } else {
+            assertThat(loadCalls, equalTo(singletonList(asList("A", "B", "A"))));
+        }
     }
 
-    @Test
-    public void should_work_with_duplicate_keys_when_caching_enabled() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_work_with_duplicate_keys_when_caching_enabled(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<String>> loadCalls = new ArrayList<>();
         DataLoader<String, String> identityLoader =
-                idLoader(newOptions().setCachingEnabled(true), loadCalls);
+                factory.idLoader(newOptions().setCachingEnabled(true), loadCalls);
 
         CompletableFuture<String> future1 = identityLoader.load("A");
         CompletableFuture<String> future2 = identityLoader.load("B");
@@ -687,17 +823,18 @@ public void should_work_with_duplicate_keys_when_caching_enabled() throws Execut
 
     // It is resilient to job queue ordering
 
-    @Test
-    public void should_Accept_objects_with_a_complex_key() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Accept_objects_with_a_complex_key(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<JsonObject>> loadCalls = new ArrayList<>();
         DataLoaderOptions options = newOptions().setCacheKeyFunction(getJsonObjectCacheMapFn());
-        DataLoader<JsonObject, Integer> identityLoader = idLoader(options, loadCalls);
+        DataLoader<JsonObject, JsonObject> identityLoader = factory.idLoader(options, loadCalls);
 
         JsonObject key1 = new JsonObject().put("id", 123);
         JsonObject key2 = new JsonObject().put("id", 123);
 
-        CompletableFuture<Integer> future1 = identityLoader.load(key1);
-        CompletableFuture<Integer> future2 = identityLoader.load(key2);
+        CompletableFuture<JsonObject> future1 = identityLoader.load(key1);
+        CompletableFuture<JsonObject> future2 = identityLoader.load(key2);
         identityLoader.dispatch();
 
         await().until(() -> future1.isDone() && future2.isDone());
@@ -708,22 +845,23 @@ public void should_Accept_objects_with_a_complex_key() throws ExecutionException
 
     // Helper methods
 
-    @Test
-    public void should_Clear_objects_with_complex_key() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Clear_objects_with_complex_key(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<JsonObject>> loadCalls = new ArrayList<>();
         DataLoaderOptions options = newOptions().setCacheKeyFunction(getJsonObjectCacheMapFn());
-        DataLoader<JsonObject, Integer> identityLoader = idLoader(options, loadCalls);
+        DataLoader<JsonObject, JsonObject> identityLoader = factory.idLoader(options, loadCalls);
 
         JsonObject key1 = new JsonObject().put("id", 123);
         JsonObject key2 = new JsonObject().put("id", 123);
 
-        CompletableFuture<Integer> future1 = identityLoader.load(key1);
+        CompletableFuture<JsonObject> future1 = identityLoader.load(key1);
         identityLoader.dispatch();
 
         await().until(future1::isDone);
         identityLoader.clear(key2); // clear equivalent object key
 
-        CompletableFuture<Integer> future2 = identityLoader.load(key1);
+        CompletableFuture<JsonObject> future2 = identityLoader.load(key1);
         identityLoader.dispatch();
 
         await().until(future2::isDone);
@@ -732,33 +870,35 @@ public void should_Clear_objects_with_complex_key() throws ExecutionException, I
         assertThat(future2.get(), equalTo(key1));
     }
 
-    @Test
-    public void should_Accept_objects_with_different_order_of_keys() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Accept_objects_with_different_order_of_keys(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<JsonObject>> loadCalls = new ArrayList<>();
         DataLoaderOptions options = newOptions().setCacheKeyFunction(getJsonObjectCacheMapFn());
-        DataLoader<JsonObject, Integer> identityLoader = idLoader(options, loadCalls);
+        DataLoader<JsonObject, JsonObject> identityLoader = factory.idLoader(options, loadCalls);
 
         JsonObject key1 = new JsonObject().put("a", 123).put("b", 321);
         JsonObject key2 = new JsonObject().put("b", 321).put("a", 123);
 
         // Fetches as expected
 
-        CompletableFuture<Integer> future1 = identityLoader.load(key1);
-        CompletableFuture<Integer> future2 = identityLoader.load(key2);
+        CompletableFuture<JsonObject> future1 = identityLoader.load(key1);
+        CompletableFuture<JsonObject> future2 = identityLoader.load(key2);
         identityLoader.dispatch();
 
         await().until(() -> future1.isDone() && future2.isDone());
         assertThat(loadCalls, equalTo(singletonList(singletonList(key1))));
         assertThat(loadCalls.size(), equalTo(1));
         assertThat(future1.get(), equalTo(key1));
-        assertThat(future2.get(), equalTo(key1));
+        assertThat(future2.get(), equalTo(key2));
     }
 
-    @Test
-    public void should_Allow_priming_the_cache_with_an_object_key() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Allow_priming_the_cache_with_an_object_key(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         List<Collection<JsonObject>> loadCalls = new ArrayList<>();
         DataLoaderOptions options = newOptions().setCacheKeyFunction(getJsonObjectCacheMapFn());
-        DataLoader<JsonObject, JsonObject> identityLoader = idLoader(options, loadCalls);
+        DataLoader<JsonObject, JsonObject> identityLoader = factory.idLoader(options, loadCalls);
 
         JsonObject key1 = new JsonObject().put("id", 123);
         JsonObject key2 = new JsonObject().put("id", 123);
@@ -775,12 +915,13 @@ public void should_Allow_priming_the_cache_with_an_object_key() throws Execution
         assertThat(future2.get(), equalTo(key1));
     }
 
-    @Test
-    public void should_Accept_a_custom_cache_map_implementation() throws ExecutionException, InterruptedException {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Accept_a_custom_cache_map_implementation(TestDataLoaderFactory factory) throws ExecutionException, InterruptedException {
         CustomCacheMap customMap = new CustomCacheMap();
         List<Collection<String>> loadCalls = new ArrayList<>();
         DataLoaderOptions options = newOptions().setCacheMap(customMap);
-        DataLoader<String, String> identityLoader = idLoader(options, loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(options, loadCalls);
 
         // Fetches as expected
 
@@ -826,11 +967,27 @@ public void should_Accept_a_custom_cache_map_implementation() throws ExecutionEx
         assertArrayEquals(customMap.stash.keySet().toArray(), emptyList().toArray());
     }
 
-    @Test
-    public void batching_disabled_should_dispatch_immediately() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_degrade_gracefully_if_cache_get_throws(TestDataLoaderFactory factory) {
+        CacheMap<String, Object> cache = new ThrowingCacheMap();
+        DataLoaderOptions options = newOptions().setCachingEnabled(true).setCacheMap(cache);
+        List<Collection<String>> loadCalls = new ArrayList<>();
+        DataLoader<String, String> identityLoader = factory.idLoader(options, loadCalls);
+
+        assertThat(identityLoader.getIfPresent("a"), equalTo(Optional.empty()));
+
+        CompletableFuture<String> future = identityLoader.load("a");
+        identityLoader.dispatch();
+        assertThat(future.join(), equalTo("a"));
+    }
+
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void batching_disabled_should_dispatch_immediately(TestDataLoaderFactory factory) {
         List<Collection<String>> loadCalls = new ArrayList<>();
         DataLoaderOptions options = newOptions().setBatchingEnabled(false);
-        DataLoader<String, String> identityLoader = idLoader(options, loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(options, loadCalls);
 
         CompletableFuture<String> fa = identityLoader.load("A");
         CompletableFuture<String> fb = identityLoader.load("B");
@@ -854,11 +1011,12 @@ public void batching_disabled_should_dispatch_immediately() {
 
     }
 
-    @Test
-    public void batching_disabled_and_caching_disabled_should_dispatch_immediately_and_forget() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void batching_disabled_and_caching_disabled_should_dispatch_immediately_and_forget(TestDataLoaderFactory factory) {
         List<Collection<String>> loadCalls = new ArrayList<>();
         DataLoaderOptions options = newOptions().setBatchingEnabled(false).setCachingEnabled(false);
-        DataLoader<String, String> identityLoader = idLoader(options, loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(options, loadCalls);
 
         CompletableFuture<String> fa = identityLoader.load("A");
         CompletableFuture<String> fb = identityLoader.load("B");
@@ -885,10 +1043,11 @@ public void batching_disabled_and_caching_disabled_should_dispatch_immediately_a
 
     }
 
-    @Test
-    public void batches_multiple_requests_with_max_batch_size() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void batches_multiple_requests_with_max_batch_size(TestDataLoaderFactory factory) {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> identityLoader = idLoader(newOptions().setMaxBatchSize(2), loadCalls);
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(newOptions().setMaxBatchSize(2), loadCalls);
 
         CompletableFuture<Integer> f1 = identityLoader.load(1);
         CompletableFuture<Integer> f2 = identityLoader.load(2);
@@ -896,7 +1055,7 @@ public void batches_multiple_requests_with_max_batch_size() {
 
         identityLoader.dispatch();
 
-        CompletableFuture.allOf(f1, f2, f3).join();
+        allOf(f1, f2, f3).join();
 
         assertThat(f1.join(), equalTo(1));
         assertThat(f2.join(), equalTo(2));
@@ -906,10 +1065,11 @@ public void batches_multiple_requests_with_max_batch_size() {
 
     }
 
-    @Test
-    public void can_split_max_batch_sizes_correctly() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void can_split_max_batch_sizes_correctly(TestDataLoaderFactory factory) {
         List<Collection<Integer>> loadCalls = new ArrayList<>();
-        DataLoader<Integer, Integer> identityLoader = idLoader(newOptions().setMaxBatchSize(5), loadCalls);
+        DataLoader<Integer, Integer> identityLoader = factory.idLoader(newOptions().setMaxBatchSize(5), loadCalls);
 
         for (int i = 0; i < 21; i++) {
             identityLoader.load(i);
@@ -928,22 +1088,23 @@ public void can_split_max_batch_sizes_correctly() {
 
     }
 
-    @Test
-    public void should_Batch_loads_occurring_within_futures() {
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_Batch_loads_occurring_within_futures(TestDataLoaderFactory factory) {
         List<Collection<String>> loadCalls = new ArrayList<>();
-        DataLoader<String, String> identityLoader = idLoader(newOptions(), loadCalls);
+        DataLoader<String, String> identityLoader = factory.idLoader(newOptions(), loadCalls);
 
         Supplier<Object> nullValue = () -> null;
 
         AtomicBoolean v4Called = new AtomicBoolean();
 
-        CompletableFuture.supplyAsync(nullValue).thenAccept(v1 -> {
+        supplyAsync(nullValue).thenAccept(v1 -> {
             identityLoader.load("a");
-            CompletableFuture.supplyAsync(nullValue).thenAccept(v2 -> {
+            supplyAsync(nullValue).thenAccept(v2 -> {
                 identityLoader.load("b");
-                CompletableFuture.supplyAsync(nullValue).thenAccept(v3 -> {
+                supplyAsync(nullValue).thenAccept(v3 -> {
                     identityLoader.load("c");
-                    CompletableFuture.supplyAsync(nullValue).thenAccept(
+                    supplyAsync(nullValue).thenAccept(
                             v4 -> {
                                 identityLoader.load("d");
                                 v4Called.set(true);
@@ -960,12 +1121,101 @@ public void should_Batch_loads_occurring_within_futures() {
                 singletonList(asList("a", "b", "c", "d"))));
     }
 
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void should_blowup_after_N_keys(TestDataLoaderFactory factory) {
+        if (!(factory instanceof TestReactiveDataLoaderFactory)) {
+            return;
+        }
+        //
+        // if we blow up after emitting N keys, the N keys should work but the rest of the keys
+        // should be exceptional
+        DataLoader<Integer, Integer> identityLoader = ((TestReactiveDataLoaderFactory) factory).idLoaderBlowsUpsAfterN(3, new DataLoaderOptions(), new ArrayList<>());
+        CompletableFuture<Integer> cf1 = identityLoader.load(1);
+        CompletableFuture<Integer> cf2 = identityLoader.load(2);
+        CompletableFuture<Integer> cf3 = identityLoader.load(3);
+        CompletableFuture<Integer> cf4 = identityLoader.load(4);
+        CompletableFuture<Integer> cf5 = identityLoader.load(5);
+        identityLoader.dispatch();
+        await().until(cf5::isDone);
+
+        assertThat(cf1.join(), equalTo(1));
+        assertThat(cf2.join(), equalTo(2));
+        assertThat(cf3.join(), equalTo(3));
+        assertThat(cf4.isCompletedExceptionally(), is(true));
+        assertThat(cf5.isCompletedExceptionally(), is(true));
+
+    }
+
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void when_values_size_are_less_then_key_size(TestDataLoaderFactory factory) {
+        //
+        // what happens if we want 4 values but are only given 2 back say
+        //
+        DataLoader<String, String> identityLoader = factory.onlyReturnsNValues(2, new DataLoaderOptions(), new ArrayList<>());
+        CompletableFuture<String> cf1 = identityLoader.load("A");
+        CompletableFuture<String> cf2 = identityLoader.load("B");
+        CompletableFuture<String> cf3 = identityLoader.load("C");
+        CompletableFuture<String> cf4 = identityLoader.load("D");
+        identityLoader.dispatch();
+
+        await().atMost(Duration.FIVE_SECONDS).until(() -> areAllDone(cf1, cf2, cf3, cf4));
+
+        if (factory instanceof ListDataLoaderFactory) {
+            assertThat(cause(cf1), instanceOf(DataLoaderAssertionException.class));
+            assertThat(cause(cf2), instanceOf(DataLoaderAssertionException.class));
+            assertThat(cause(cf3), instanceOf(DataLoaderAssertionException.class));
+            assertThat(cause(cf4), instanceOf(DataLoaderAssertionException.class));
+        } else if (factory instanceof PublisherDataLoaderFactory) {
+            // some have completed progressively but the other never did
+            assertThat(cf1.join(), equalTo("A"));
+            assertThat(cf2.join(), equalTo("B"));
+            assertThat(cause(cf3), instanceOf(DataLoaderAssertionException.class));
+            assertThat(cause(cf4), instanceOf(DataLoaderAssertionException.class));
+        } else {
+            // with the maps it's ok to have fewer results
+            assertThat(cf1.join(), equalTo("A"));
+            assertThat(cf2.join(), equalTo("B"));
+            assertThat(cf3.join(), equalTo(null));
+            assertThat(cf4.join(), equalTo(null));
+        }
+    }
+
+    @ParameterizedTest
+    @MethodSource("dataLoaderFactories")
+    public void when_values_size_are_more_then_key_size(TestDataLoaderFactory factory) {
+        //
+        // what happens if we want 4 values but only given 6 back say
+        //
+        DataLoader<String, String> identityLoader = factory.idLoaderReturnsTooMany(2, new DataLoaderOptions(), new ArrayList<>());
+        CompletableFuture<String> cf1 = identityLoader.load("A");
+        CompletableFuture<String> cf2 = identityLoader.load("B");
+        CompletableFuture<String> cf3 = identityLoader.load("C");
+        CompletableFuture<String> cf4 = identityLoader.load("D");
+        identityLoader.dispatch();
+        await().atMost(Duration.FIVE_SECONDS).until(() -> areAllDone(cf1, cf2, cf3, cf4));
+
+
+        if (factory instanceof ListDataLoaderFactory) {
+            assertThat(cause(cf1), instanceOf(DataLoaderAssertionException.class));
+            assertThat(cause(cf2), instanceOf(DataLoaderAssertionException.class));
+            assertThat(cause(cf3), instanceOf(DataLoaderAssertionException.class));
+            assertThat(cause(cf4), instanceOf(DataLoaderAssertionException.class));
+        } else {
+            assertThat(cf1.join(), equalTo("A"));
+            assertThat(cf2.join(), equalTo("B"));
+            assertThat(cf3.join(), equalTo("C"));
+            assertThat(cf4.join(), equalTo("D"));
+        }
+    }
+
     @Test
     public void can_call_a_loader_from_a_loader() throws Exception {
         List<Collection<String>> deepLoadCalls = new ArrayList<>();
         DataLoader<String, String> deepLoader = newDataLoader(keys -> {
             deepLoadCalls.add(keys);
-            return CompletableFuture.completedFuture(keys);
+            return completedFuture(keys);
         });
 
         List<Collection<String>> aLoadCalls = new ArrayList<>();
@@ -985,7 +1235,7 @@ public void can_call_a_loader_from_a_loader() throws Exception {
         CompletableFuture<String> b1 = bLoader.load("B1");
         CompletableFuture<String> b2 = bLoader.load("B2");
 
-        CompletableFuture.allOf(
+        allOf(
                 aLoader.dispatch(),
                 deepLoader.dispatch(),
                 bLoader.dispatch(),
@@ -1011,11 +1261,10 @@ public void can_call_a_loader_from_a_loader() throws Exception {
     public void should_allow_composition_of_data_loader_calls() {
         UserManager userManager = new UserManager();
 
-        BatchLoader<Long, User> userBatchLoader = userIds -> CompletableFuture
-                .supplyAsync(() -> userIds
-                        .stream()
-                        .map(userManager::loadUserById)
-                        .collect(Collectors.toList()));
+        BatchLoader<Long, User> userBatchLoader = userIds -> supplyAsync(() -> userIds
+                .stream()
+                .map(userManager::loadUserById)
+                .collect(Collectors.toList()));
         DataLoader<Long, User> userLoader = newDataLoader(userBatchLoader);
 
         AtomicBoolean gandalfCalled = new AtomicBoolean(false);
@@ -1051,56 +1300,21 @@ private static CacheKey<JsonObject> getJsonObjectCacheMapFn() {
                 .collect(Collectors.joining());
     }
 
-    private static <K, V> DataLoader<K, V> idLoader(DataLoaderOptions options, List<Collection<K>> loadCalls) {
-        return newDataLoader(keys -> {
-            loadCalls.add(new ArrayList<>(keys));
-            @SuppressWarnings("unchecked")
-            List<V> values = keys.stream()
-                    .map(k -> (V) k)
-                    .collect(Collectors.toList());
-            return CompletableFuture.completedFuture(values);
-        }, options);
-    }
-
-    private static <K, V> DataLoader<K, V> idLoaderBlowsUps(
-            DataLoaderOptions options, List<Collection<K>> loadCalls) {
-        return newDataLoader(keys -> {
-            loadCalls.add(new ArrayList<>(keys));
-            return TestKit.futureError();
-        }, options);
-    }
-
-    private static <K> DataLoader<K, Object> idLoaderAllExceptions(
-            DataLoaderOptions options, List<Collection<K>> loadCalls) {
-        return newDataLoader(keys -> {
-            loadCalls.add(new ArrayList<>(keys));
+    private static class ThrowingCacheMap extends CustomCacheMap {
 
-            List<Object> errors = keys.stream().map(k -> new IllegalStateException("Error")).collect(Collectors.toList());
-            return CompletableFuture.completedFuture(errors);
-        }, options);
-    }
-
-    private static DataLoader<Integer, Object> idLoaderOddEvenExceptions(
-            DataLoaderOptions options, List<Collection<Integer>> loadCalls) {
-        return newDataLoader(keys -> {
-            loadCalls.add(new ArrayList<>(keys));
-
-            List<Object> errors = new ArrayList<>();
-            for (Integer key : keys) {
-                if (key % 2 == 0) {
-                    errors.add(key);
-                } else {
-                    errors.add(new IllegalStateException("Error"));
-                }
-            }
-            return CompletableFuture.completedFuture(errors);
-        }, options);
+        @Override
+        public CompletableFuture<Object> get(String key) {
+            throw new RuntimeException("Cache implementation failed.");
+        }
     }
 
-
-    private <T> BatchLoader<T, T> keysAsValues() {
-        return CompletableFuture::completedFuture;
+    private static Stream<Arguments> dataLoaderFactories() {
+        return Stream.of(
+                Arguments.of(Named.of("List DataLoader", new ListDataLoaderFactory())),
+                Arguments.of(Named.of("Mapped DataLoader", new MappedDataLoaderFactory())),
+                Arguments.of(Named.of("Publisher DataLoader", new PublisherDataLoaderFactory())),
+                Arguments.of(Named.of("Mapped Publisher DataLoader", new MappedPublisherDataLoaderFactory()))
+        );
     }
-
 }
 
diff --git a/src/test/java/org/dataloader/DataLoaderTimeTest.java b/src/test/java/org/dataloader/DataLoaderTimeTest.java
index ee73d85..b4d645c 100644
--- a/src/test/java/org/dataloader/DataLoaderTimeTest.java
+++ b/src/test/java/org/dataloader/DataLoaderTimeTest.java
@@ -1,13 +1,13 @@
 package org.dataloader;
 
 import org.dataloader.fixtures.TestingClock;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.time.Instant;
 
 import static org.dataloader.fixtures.TestKit.keysAsValues;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertThat;
 
 @SuppressWarnings("UnusedReturnValue")
 public class DataLoaderTimeTest {
diff --git a/src/test/java/org/dataloader/DataLoaderValueCacheTest.java b/src/test/java/org/dataloader/DataLoaderValueCacheTest.java
index 2716fae..1fb5ea2 100644
--- a/src/test/java/org/dataloader/DataLoaderValueCacheTest.java
+++ b/src/test/java/org/dataloader/DataLoaderValueCacheTest.java
@@ -5,7 +5,7 @@
 import org.dataloader.fixtures.CaffeineValueCache;
 import org.dataloader.fixtures.CustomValueCache;
 import org.dataloader.impl.DataLoaderAssertionException;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -22,11 +22,11 @@
 import static org.dataloader.fixtures.TestKit.snooze;
 import static org.dataloader.fixtures.TestKit.sort;
 import static org.dataloader.impl.CompletableFutureKit.failedFuture;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertArrayEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class DataLoaderValueCacheTest {
 
diff --git a/src/test/java/org/dataloader/DataLoaderWithTryTest.java b/src/test/java/org/dataloader/DataLoaderWithTryTest.java
index e9e8538..fda7bd4 100644
--- a/src/test/java/org/dataloader/DataLoaderWithTryTest.java
+++ b/src/test/java/org/dataloader/DataLoaderWithTryTest.java
@@ -1,7 +1,7 @@
 package org.dataloader;
 
 import org.hamcrest.Matchers;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -12,9 +12,9 @@
 import static java.util.Arrays.asList;
 import static java.util.Collections.singletonList;
 import static org.dataloader.DataLoaderFactory.*;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.nullValue;
-import static org.junit.Assert.assertThat;
 
 public class DataLoaderWithTryTest {
 
diff --git a/src/test/java/org/dataloader/TryTest.java b/src/test/java/org/dataloader/TryTest.java
index 4da7bca..1b237e2 100644
--- a/src/test/java/org/dataloader/TryTest.java
+++ b/src/test/java/org/dataloader/TryTest.java
@@ -1,7 +1,7 @@
 package org.dataloader;
 
-import org.junit.Assert;
-import org.junit.Test;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
 
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
@@ -9,11 +9,11 @@
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Function;
 
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.nullValue;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class TryTest {
 
@@ -29,7 +29,7 @@ private void expectThrowable(RunThatCanThrow runnable, Class<? extends Throwable
                 return;
             }
         }
-        Assert.fail("Expected throwable :  " + throwableClass.getName());
+        Assertions.fail("Expected throwable :  " + throwableClass.getName());
     }
 
     @SuppressWarnings("SameParameterValue")
diff --git a/src/test/java/org/dataloader/fixtures/TestKit.java b/src/test/java/org/dataloader/fixtures/TestKit.java
index adffb06..c22988d 100644
--- a/src/test/java/org/dataloader/fixtures/TestKit.java
+++ b/src/test/java/org/dataloader/fixtures/TestKit.java
@@ -131,4 +131,13 @@ public static <T> Set<T> asSet(T... elements) {
     public static <T> Set<T> asSet(Collection<T> elements) {
         return new LinkedHashSet<>(elements);
     }
+
+    public static boolean areAllDone(CompletableFuture<?>... cfs) {
+        for (CompletableFuture<?> cf : cfs) {
+            if (! cf.isDone()) {
+                return false;
+            }
+        }
+        return true;
+    }
 }
diff --git a/src/test/java/org/dataloader/fixtures/UserManager.java b/src/test/java/org/dataloader/fixtures/UserManager.java
index 24fee0d..1d2ff1f 100644
--- a/src/test/java/org/dataloader/fixtures/UserManager.java
+++ b/src/test/java/org/dataloader/fixtures/UserManager.java
@@ -1,5 +1,8 @@
 package org.dataloader.fixtures;
 
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -52,6 +55,14 @@ public List<User> loadUsersById(List<Long> userIds) {
         return userIds.stream().map(this::loadUserById).collect(Collectors.toList());
     }
 
+    public Publisher<User> streamUsersById(List<Long> userIds) {
+        return Flux.fromIterable(loadUsersById(userIds));
+    }
+
+    public Publisher<Map.Entry<Long, User>> streamUsersById(Set<Long> userIds) {
+        return Flux.fromIterable(loadMapOfUsersByIds(null, userIds).entrySet());
+    }
+
     public Map<Long, User> loadMapOfUsersByIds(SecurityCtx callCtx, Set<Long> userIds) {
         Map<Long, User> map = new HashMap<>();
         userIds.forEach(userId -> {
diff --git a/src/test/java/org/dataloader/fixtures/parameterized/ListDataLoaderFactory.java b/src/test/java/org/dataloader/fixtures/parameterized/ListDataLoaderFactory.java
new file mode 100644
index 0000000..ee1f1d7
--- /dev/null
+++ b/src/test/java/org/dataloader/fixtures/parameterized/ListDataLoaderFactory.java
@@ -0,0 +1,79 @@
+package org.dataloader.fixtures.parameterized;
+
+import org.dataloader.DataLoader;
+import org.dataloader.DataLoaderOptions;
+import org.dataloader.fixtures.TestKit;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static java.util.concurrent.CompletableFuture.completedFuture;
+import static org.dataloader.DataLoaderFactory.newDataLoader;
+
+public class ListDataLoaderFactory implements TestDataLoaderFactory {
+    @Override
+    public <K> DataLoader<K, K> idLoader(DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+            return completedFuture(keys);
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, K> idLoaderBlowsUps(
+            DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+            return TestKit.futureError();
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, Object> idLoaderAllExceptions(DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<Object> errors = keys.stream().map(k -> new IllegalStateException("Error")).collect(Collectors.toList());
+            return completedFuture(errors);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<Integer, Object> idLoaderOddEvenExceptions(DataLoaderOptions options, List<Collection<Integer>> loadCalls) {
+        return newDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<Object> errors = new ArrayList<>();
+            for (Integer key : keys) {
+                if (key % 2 == 0) {
+                    errors.add(key);
+                } else {
+                    errors.add(new IllegalStateException("Error"));
+                }
+            }
+            return completedFuture(errors);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<String, String> onlyReturnsNValues(int N, DataLoaderOptions options, ArrayList<Object> loadCalls) {
+        return newDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+            return completedFuture(keys.subList(0, N));
+        }, options);
+    }
+
+    @Override
+    public DataLoader<String, String> idLoaderReturnsTooMany(int howManyMore, DataLoaderOptions options, ArrayList<Object> loadCalls) {
+        return newDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+            List<String> l = new ArrayList<>(keys);
+            for (int i = 0; i < howManyMore; i++) {
+                l.add("extra-" + i);
+            }
+            return completedFuture(l);
+        }, options);
+    }
+}
diff --git a/src/test/java/org/dataloader/fixtures/parameterized/MappedDataLoaderFactory.java b/src/test/java/org/dataloader/fixtures/parameterized/MappedDataLoaderFactory.java
new file mode 100644
index 0000000..8f41441
--- /dev/null
+++ b/src/test/java/org/dataloader/fixtures/parameterized/MappedDataLoaderFactory.java
@@ -0,0 +1,95 @@
+package org.dataloader.fixtures.parameterized;
+
+import org.dataloader.DataLoader;
+import org.dataloader.DataLoaderOptions;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import static java.util.concurrent.CompletableFuture.completedFuture;
+import static org.dataloader.DataLoaderFactory.newMappedDataLoader;
+import static org.dataloader.fixtures.TestKit.futureError;
+
+public class MappedDataLoaderFactory implements TestDataLoaderFactory {
+
+    @Override
+    public <K> DataLoader<K, K> idLoader(
+            DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newMappedDataLoader((keys) -> {
+            loadCalls.add(new ArrayList<>(keys));
+            Map<K, K> map = new HashMap<>();
+            keys.forEach(k -> map.put(k, k));
+            return completedFuture(map);
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, K> idLoaderBlowsUps(DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newMappedDataLoader((keys) -> {
+            loadCalls.add(new ArrayList<>(keys));
+            return futureError();
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, Object> idLoaderAllExceptions(
+            DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newMappedDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+            Map<K, Object> errorByKey = new HashMap<>();
+            keys.forEach(k -> errorByKey.put(k, new IllegalStateException("Error")));
+            return completedFuture(errorByKey);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<Integer, Object> idLoaderOddEvenExceptions(
+            DataLoaderOptions options, List<Collection<Integer>> loadCalls) {
+        return newMappedDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            Map<Integer, Object> errorByKey = new HashMap<>();
+            for (Integer key : keys) {
+                if (key % 2 == 0) {
+                    errorByKey.put(key, key);
+                } else {
+                    errorByKey.put(key, new IllegalStateException("Error"));
+                }
+            }
+            return completedFuture(errorByKey);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<String, String> onlyReturnsNValues(int N, DataLoaderOptions options, ArrayList<Object> loadCalls) {
+        return newMappedDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            Map<String, String> collect = List.copyOf(keys).subList(0, N).stream().collect(Collectors.toMap(
+                    k -> k, v -> v
+            ));
+            return completedFuture(collect);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<String, String> idLoaderReturnsTooMany(int howManyMore, DataLoaderOptions options, ArrayList<Object> loadCalls) {
+        return newMappedDataLoader(keys -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<String> l = new ArrayList<>(keys);
+            for (int i = 0; i < howManyMore; i++) {
+                l.add("extra-" + i);
+            }
+
+            Map<String, String> collect = l.stream().collect(Collectors.toMap(
+                    k -> k, v -> v
+            ));
+            return completedFuture(collect);
+        }, options);
+    }
+}
diff --git a/src/test/java/org/dataloader/fixtures/parameterized/MappedPublisherDataLoaderFactory.java b/src/test/java/org/dataloader/fixtures/parameterized/MappedPublisherDataLoaderFactory.java
new file mode 100644
index 0000000..9c92330
--- /dev/null
+++ b/src/test/java/org/dataloader/fixtures/parameterized/MappedPublisherDataLoaderFactory.java
@@ -0,0 +1,108 @@
+package org.dataloader.fixtures.parameterized;
+
+import org.dataloader.DataLoader;
+import org.dataloader.DataLoaderOptions;
+import org.dataloader.Try;
+import reactor.core.publisher.Flux;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toSet;
+import static org.dataloader.DataLoaderFactory.newMappedPublisherDataLoader;
+import static org.dataloader.DataLoaderFactory.newMappedPublisherDataLoaderWithTry;
+
+public class MappedPublisherDataLoaderFactory implements TestDataLoaderFactory, TestReactiveDataLoaderFactory {
+
+    @Override
+    public <K> DataLoader<K, K> idLoader(
+            DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newMappedPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+            Map<K, K> map = new HashMap<>();
+            keys.forEach(k -> map.put(k, k));
+            Flux.fromIterable(map.entrySet()).subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, K> idLoaderBlowsUps(DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newMappedPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+            Flux.<Map.Entry<K, K>>error(new IllegalStateException("Error")).subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, Object> idLoaderAllExceptions(
+            DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newMappedPublisherDataLoaderWithTry((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+            Stream<Map.Entry<K, Try<Object>>> failures = keys.stream().map(k -> Map.entry(k, Try.failed(new IllegalStateException("Error"))));
+            Flux.fromStream(failures).subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<Integer, Object> idLoaderOddEvenExceptions(
+            DataLoaderOptions options, List<Collection<Integer>> loadCalls) {
+        return newMappedPublisherDataLoaderWithTry((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            Map<Integer, Try<Object>> errorByKey = new HashMap<>();
+            for (Integer key : keys) {
+                if (key % 2 == 0) {
+                    errorByKey.put(key, Try.succeeded(key));
+                } else {
+                    errorByKey.put(key, Try.failed(new IllegalStateException("Error")));
+                }
+            }
+            Flux.fromIterable(errorByKey.entrySet()).subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, K> idLoaderBlowsUpsAfterN(int N, DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newMappedPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<K> nKeys = keys.stream().limit(N).collect(toList());
+            Flux<Map.Entry<K, K>> subFlux = Flux.fromIterable(nKeys).map(k -> Map.entry(k, k));
+            subFlux.concatWith(Flux.error(new IllegalStateException("Error")))
+                    .subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<String, String> onlyReturnsNValues(int N, DataLoaderOptions options, ArrayList<Object> loadCalls) {
+        return newMappedPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<String> nKeys = keys.stream().limit(N).collect(toList());
+            Flux.fromIterable(nKeys).map(k -> Map.entry(k, k))
+                    .subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<String, String> idLoaderReturnsTooMany(int howManyMore, DataLoaderOptions options, ArrayList<Object> loadCalls) {
+        return newMappedPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<String> l = new ArrayList<>(keys);
+            for (int i = 0; i < howManyMore; i++) {
+                l.add("extra-" + i);
+            }
+
+            Flux.fromIterable(l).map(k -> Map.entry(k, k))
+                    .subscribe(subscriber);
+        }, options);
+    }
+}
diff --git a/src/test/java/org/dataloader/fixtures/parameterized/PublisherDataLoaderFactory.java b/src/test/java/org/dataloader/fixtures/parameterized/PublisherDataLoaderFactory.java
new file mode 100644
index 0000000..d75ff38
--- /dev/null
+++ b/src/test/java/org/dataloader/fixtures/parameterized/PublisherDataLoaderFactory.java
@@ -0,0 +1,100 @@
+package org.dataloader.fixtures.parameterized;
+
+import org.dataloader.DataLoader;
+import org.dataloader.DataLoaderOptions;
+import org.dataloader.Try;
+import reactor.core.publisher.Flux;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.dataloader.DataLoaderFactory.newPublisherDataLoader;
+import static org.dataloader.DataLoaderFactory.newPublisherDataLoaderWithTry;
+
+public class PublisherDataLoaderFactory implements TestDataLoaderFactory, TestReactiveDataLoaderFactory {
+
+    @Override
+    public <K> DataLoader<K, K> idLoader(
+            DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+            Flux.fromIterable(keys).subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, K> idLoaderBlowsUps(DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+            Flux.<K>error(new IllegalStateException("Error")).subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, Object> idLoaderAllExceptions(
+            DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newPublisherDataLoaderWithTry((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+            Stream<Try<Object>> failures = keys.stream().map(k -> Try.failed(new IllegalStateException("Error")));
+            Flux.fromStream(failures).subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<Integer, Object> idLoaderOddEvenExceptions(
+            DataLoaderOptions options, List<Collection<Integer>> loadCalls) {
+        return newPublisherDataLoaderWithTry((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<Try<Object>> errors = new ArrayList<>();
+            for (Integer key : keys) {
+                if (key % 2 == 0) {
+                    errors.add(Try.succeeded(key));
+                } else {
+                    errors.add(Try.failed(new IllegalStateException("Error")));
+                }
+            }
+            Flux.fromIterable(errors).subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public <K> DataLoader<K, K> idLoaderBlowsUpsAfterN(int N, DataLoaderOptions options, List<Collection<K>> loadCalls) {
+        return newPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<K> nKeys = keys.subList(0, N);
+            Flux<K> subFlux = Flux.fromIterable(nKeys);
+            subFlux.concatWith(Flux.error(new IllegalStateException("Error")))
+                    .subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<String, String> onlyReturnsNValues(int N, DataLoaderOptions options, ArrayList<Object> loadCalls) {
+        return newPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<String> nKeys = keys.subList(0, N);
+            Flux.fromIterable(nKeys)
+                    .subscribe(subscriber);
+        }, options);
+    }
+
+    @Override
+    public DataLoader<String, String> idLoaderReturnsTooMany(int howManyMore, DataLoaderOptions options, ArrayList<Object> loadCalls) {
+        return newPublisherDataLoader((keys, subscriber) -> {
+            loadCalls.add(new ArrayList<>(keys));
+
+            List<String> l = new ArrayList<>(keys);
+            for (int i = 0; i < howManyMore; i++) {
+                l.add("extra-" + i);
+            }
+
+            Flux.fromIterable(l)
+                    .subscribe(subscriber);
+        }, options);
+    }
+}
diff --git a/src/test/java/org/dataloader/fixtures/parameterized/TestDataLoaderFactory.java b/src/test/java/org/dataloader/fixtures/parameterized/TestDataLoaderFactory.java
new file mode 100644
index 0000000..8c1bc22
--- /dev/null
+++ b/src/test/java/org/dataloader/fixtures/parameterized/TestDataLoaderFactory.java
@@ -0,0 +1,22 @@
+package org.dataloader.fixtures.parameterized;
+
+import org.dataloader.DataLoader;
+import org.dataloader.DataLoaderOptions;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+public interface TestDataLoaderFactory {
+    <K> DataLoader<K, K> idLoader(DataLoaderOptions options, List<Collection<K>> loadCalls);
+
+    <K> DataLoader<K, K> idLoaderBlowsUps(DataLoaderOptions options, List<Collection<K>> loadCalls);
+
+    <K> DataLoader<K, Object> idLoaderAllExceptions(DataLoaderOptions options, List<Collection<K>> loadCalls);
+
+    DataLoader<Integer, Object> idLoaderOddEvenExceptions(DataLoaderOptions options, List<Collection<Integer>> loadCalls);
+
+    DataLoader<String, String> onlyReturnsNValues(int N, DataLoaderOptions options, ArrayList<Object> loadCalls);
+
+    DataLoader<String, String> idLoaderReturnsTooMany(int howManyMore, DataLoaderOptions options, ArrayList<Object> loadCalls);
+}
diff --git a/src/test/java/org/dataloader/fixtures/parameterized/TestReactiveDataLoaderFactory.java b/src/test/java/org/dataloader/fixtures/parameterized/TestReactiveDataLoaderFactory.java
new file mode 100644
index 0000000..d45932c
--- /dev/null
+++ b/src/test/java/org/dataloader/fixtures/parameterized/TestReactiveDataLoaderFactory.java
@@ -0,0 +1,11 @@
+package org.dataloader.fixtures.parameterized;
+
+import org.dataloader.DataLoader;
+import org.dataloader.DataLoaderOptions;
+
+import java.util.Collection;
+import java.util.List;
+
+public interface TestReactiveDataLoaderFactory {
+    <K> DataLoader<K, K> idLoaderBlowsUpsAfterN(int N, DataLoaderOptions options, List<Collection<K>> loadCalls);
+}
diff --git a/src/test/java/org/dataloader/impl/PromisedValuesImplTest.java b/src/test/java/org/dataloader/impl/PromisedValuesImplTest.java
index 3c9ce65..6073319 100644
--- a/src/test/java/org/dataloader/impl/PromisedValuesImplTest.java
+++ b/src/test/java/org/dataloader/impl/PromisedValuesImplTest.java
@@ -1,6 +1,6 @@
 package org.dataloader.impl;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
 import java.util.Collections;
@@ -12,12 +12,12 @@
 import static java.util.Arrays.asList;
 import static java.util.concurrent.CompletableFuture.supplyAsync;
 import static org.awaitility.Awaitility.await;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.instanceOf;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.notNullValue;
 import static org.hamcrest.Matchers.nullValue;
-import static org.junit.Assert.assertThat;
 
 public class PromisedValuesImplTest {
 
diff --git a/src/test/java/org/dataloader/registries/DispatchPredicateTest.java b/src/test/java/org/dataloader/registries/DispatchPredicateTest.java
index f241c2f..07a7416 100644
--- a/src/test/java/org/dataloader/registries/DispatchPredicateTest.java
+++ b/src/test/java/org/dataloader/registries/DispatchPredicateTest.java
@@ -4,12 +4,12 @@
 import org.dataloader.DataLoader;
 import org.dataloader.fixtures.TestKit;
 import org.dataloader.fixtures.TestingClock;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.time.Duration;
 
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 public class DispatchPredicateTest {
 
diff --git a/src/test/java/org/dataloader/registries/ScheduledDataLoaderRegistryPredicateTest.java b/src/test/java/org/dataloader/registries/ScheduledDataLoaderRegistryPredicateTest.java
index 4eab564..94f5cff 100644
--- a/src/test/java/org/dataloader/registries/ScheduledDataLoaderRegistryPredicateTest.java
+++ b/src/test/java/org/dataloader/registries/ScheduledDataLoaderRegistryPredicateTest.java
@@ -3,7 +3,7 @@
 import org.dataloader.BatchLoader;
 import org.dataloader.DataLoader;
 import org.dataloader.DataLoaderRegistry;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.time.Duration;
 import java.util.concurrent.CompletableFuture;
@@ -12,10 +12,9 @@
 import static org.awaitility.Awaitility.await;
 import static org.dataloader.DataLoaderFactory.newDataLoader;
 import static org.dataloader.fixtures.TestKit.asSet;
-import static org.dataloader.registries.DispatchPredicate.DISPATCH_NEVER;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
-import static org.junit.Assert.assertThat;
 
 public class ScheduledDataLoaderRegistryPredicateTest {
     final BatchLoader<Object, Object> identityBatchLoader = CompletableFuture::completedFuture;
diff --git a/src/test/java/org/dataloader/registries/ScheduledDataLoaderRegistryTest.java b/src/test/java/org/dataloader/registries/ScheduledDataLoaderRegistryTest.java
index 146c186..e82205d 100644
--- a/src/test/java/org/dataloader/registries/ScheduledDataLoaderRegistryTest.java
+++ b/src/test/java/org/dataloader/registries/ScheduledDataLoaderRegistryTest.java
@@ -1,11 +1,11 @@
 package org.dataloader.registries;
 
-import junit.framework.TestCase;
 import org.awaitility.core.ConditionTimeoutException;
 import org.dataloader.DataLoader;
 import org.dataloader.DataLoaderFactory;
 import org.dataloader.DataLoaderRegistry;
 import org.dataloader.fixtures.TestKit;
+import org.junit.jupiter.api.Test;
 
 import java.time.Duration;
 import java.util.ArrayList;
@@ -22,17 +22,22 @@
 import static org.awaitility.Duration.TWO_SECONDS;
 import static org.dataloader.fixtures.TestKit.keysAsValues;
 import static org.dataloader.fixtures.TestKit.snooze;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.is;
-import static org.junit.Assert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
-public class ScheduledDataLoaderRegistryTest extends TestCase {
+public class ScheduledDataLoaderRegistryTest {
 
     DispatchPredicate alwaysDispatch = (key, dl) -> true;
     DispatchPredicate neverDispatch = (key, dl) -> false;
 
 
-    public void test_basic_setup_works_like_a_normal_dlr() {
+    @Test
+    public void basic_setup_works_like_a_normal_dlr() {
 
         List<List<String>> aCalls = new ArrayList<>();
         List<List<String>> bCalls = new ArrayList<>();
@@ -63,7 +68,8 @@ public void test_basic_setup_works_like_a_normal_dlr() {
         assertThat(bCalls, equalTo(singletonList(asList("BK1", "BK2"))));
     }
 
-    public void test_predicate_always_false() {
+    @Test
+    public void predicate_always_false() {
 
         List<List<String>> calls = new ArrayList<>();
         DataLoader<String, String> dlA = DataLoaderFactory.newDataLoader(keysAsValues(calls));
@@ -92,7 +98,8 @@ public void test_predicate_always_false() {
         assertThat(calls.size(), equalTo(0));
     }
 
-    public void test_predicate_that_eventually_returns_true() {
+    @Test
+    public void predicate_that_eventually_returns_true() {
 
 
         AtomicInteger counter = new AtomicInteger();
@@ -123,7 +130,8 @@ public void test_predicate_that_eventually_returns_true() {
         assertTrue(p2.isDone());
     }
 
-    public void test_dispatchAllWithCountImmediately() {
+    @Test
+    public void dispatchAllWithCountImmediately() {
         List<List<String>> calls = new ArrayList<>();
         DataLoader<String, String> dlA = DataLoaderFactory.newDataLoader(keysAsValues(calls));
         dlA.load("K1");
@@ -140,7 +148,8 @@ public void test_dispatchAllWithCountImmediately() {
         assertThat(calls, equalTo(singletonList(asList("K1", "K2"))));
     }
 
-    public void test_dispatchAllImmediately() {
+    @Test
+    public void dispatchAllImmediately() {
         List<List<String>> calls = new ArrayList<>();
         DataLoader<String, String> dlA = DataLoaderFactory.newDataLoader(keysAsValues(calls));
         dlA.load("K1");
@@ -156,7 +165,8 @@ public void test_dispatchAllImmediately() {
         assertThat(calls, equalTo(singletonList(asList("K1", "K2"))));
     }
 
-    public void test_rescheduleNow() {
+    @Test
+    public void rescheduleNow() {
         AtomicInteger i = new AtomicInteger();
         DispatchPredicate countingPredicate = (dataLoaderKey, dataLoader) -> i.incrementAndGet() > 5;
 
@@ -179,7 +189,8 @@ public void test_rescheduleNow() {
         assertThat(calls, equalTo(singletonList(asList("K1", "K2"))));
     }
 
-    public void test_it_will_take_out_the_schedule_once_it_dispatches() {
+    @Test
+    public void it_will_take_out_the_schedule_once_it_dispatches() {
         AtomicInteger counter = new AtomicInteger();
         DispatchPredicate countingPredicate = (dataLoaderKey, dataLoader) -> counter.incrementAndGet() > 5;
 
@@ -220,7 +231,8 @@ public void test_it_will_take_out_the_schedule_once_it_dispatches() {
         assertThat(calls, equalTo(asList(asList("K1", "K2"), asList("K3", "K4"))));
     }
 
-    public void test_close_is_a_one_way_door() {
+    @Test
+    public void close_is_a_one_way_door() {
         AtomicInteger counter = new AtomicInteger();
         DispatchPredicate countingPredicate = (dataLoaderKey, dataLoader) -> {
             counter.incrementAndGet();
@@ -264,7 +276,8 @@ public void test_close_is_a_one_way_door() {
         assertEquals(counter.get(), countThen + 1);
     }
 
-    public void test_can_tick_after_first_dispatch_for_chain_data_loaders() {
+    @Test
+    public void can_tick_after_first_dispatch_for_chain_data_loaders() {
 
         // delays much bigger than the tick rate will mean multiple calls to dispatch
         DataLoader<String, String> dlA = TestKit.idLoaderAsync(Duration.ofMillis(100));
@@ -293,7 +306,8 @@ public void test_can_tick_after_first_dispatch_for_chain_data_loaders() {
         registry.close();
     }
 
-    public void test_chain_data_loaders_will_hang_if_not_in_ticker_mode() {
+    @Test
+    public void chain_data_loaders_will_hang_if_not_in_ticker_mode() {
 
         // delays much bigger than the tick rate will mean multiple calls to dispatch
         DataLoader<String, String> dlA = TestKit.idLoaderAsync(Duration.ofMillis(100));
@@ -325,7 +339,8 @@ public void test_chain_data_loaders_will_hang_if_not_in_ticker_mode() {
         registry.close();
     }
 
-    public void test_executors_are_shutdown() {
+    @Test
+    public void executors_are_shutdown() {
         ScheduledDataLoaderRegistry registry = ScheduledDataLoaderRegistry.newScheduledRegistry().build();
 
         ScheduledExecutorService executorService = registry.getScheduledExecutorService();
@@ -345,4 +360,4 @@ public void test_executors_are_shutdown() {
 
 
     }
-}
\ No newline at end of file
+}
diff --git a/src/test/java/org/dataloader/scheduler/BatchLoaderSchedulerTest.java b/src/test/java/org/dataloader/scheduler/BatchLoaderSchedulerTest.java
index beb7c18..ff9ec8e 100644
--- a/src/test/java/org/dataloader/scheduler/BatchLoaderSchedulerTest.java
+++ b/src/test/java/org/dataloader/scheduler/BatchLoaderSchedulerTest.java
@@ -3,7 +3,7 @@
 import org.dataloader.BatchLoaderEnvironment;
 import org.dataloader.DataLoader;
 import org.dataloader.DataLoaderOptions;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.List;
 import java.util.Map;
@@ -20,8 +20,8 @@
 import static org.dataloader.fixtures.TestKit.keysAsValues;
 import static org.dataloader.fixtures.TestKit.keysAsValuesWithContext;
 import static org.dataloader.fixtures.TestKit.snooze;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertThat;
 
 public class BatchLoaderSchedulerTest {
 
@@ -36,6 +36,11 @@ public <K, V> CompletionStage<List<V>> scheduleBatchLoader(ScheduledBatchLoaderC
         public <K, V> CompletionStage<Map<K, V>> scheduleMappedBatchLoader(ScheduledMappedBatchLoaderCall<K, V> scheduledCall, List<K> keys, BatchLoaderEnvironment environment) {
             return scheduledCall.invoke();
         }
+
+        @Override
+        public <K> void scheduleBatchPublisher(ScheduledBatchPublisherCall scheduledCall, List<K> keys, BatchLoaderEnvironment environment) {
+            scheduledCall.invoke();
+        }
     };
 
     private BatchLoaderScheduler delayedScheduling(int ms) {
@@ -56,6 +61,12 @@ public <K, V> CompletionStage<Map<K, V>> scheduleMappedBatchLoader(ScheduledMapp
                     return scheduledCall.invoke();
                 }).thenCompose(Function.identity());
             }
+
+            @Override
+            public <K> void scheduleBatchPublisher(ScheduledBatchPublisherCall scheduledCall, List<K> keys, BatchLoaderEnvironment environment) {
+                snooze(ms);
+                scheduledCall.invoke();
+            }
         };
     }
 
@@ -139,6 +150,15 @@ public <K, V> CompletionStage<Map<K, V>> scheduleMappedBatchLoader(ScheduledMapp
                     return scheduledCall.invoke();
                 }).thenCompose(Function.identity());
             }
+
+            @Override
+            public <K> void scheduleBatchPublisher(ScheduledBatchPublisherCall scheduledCall, List<K> keys, BatchLoaderEnvironment environment) {
+                CompletableFuture.supplyAsync(() -> {
+                    snooze(10);
+                    scheduledCall.invoke();
+                    return null;
+                });
+            }
         };
         DataLoaderOptions options = DataLoaderOptions.newOptions().setBatchLoaderScheduler(funkyScheduler);
 
diff --git a/src/test/java/org/dataloader/stats/StatisticsCollectorTest.java b/src/test/java/org/dataloader/stats/StatisticsCollectorTest.java
index fbfd5e2..f1cc8d8 100644
--- a/src/test/java/org/dataloader/stats/StatisticsCollectorTest.java
+++ b/src/test/java/org/dataloader/stats/StatisticsCollectorTest.java
@@ -5,13 +5,13 @@
 import org.dataloader.stats.context.IncrementCacheHitCountStatisticsContext;
 import org.dataloader.stats.context.IncrementLoadCountStatisticsContext;
 import org.dataloader.stats.context.IncrementLoadErrorCountStatisticsContext;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.concurrent.CompletableFuture;
 
 import static java.util.Collections.singletonList;
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertThat;
 
 public class StatisticsCollectorTest {
 
diff --git a/src/test/java/org/dataloader/stats/StatisticsTest.java b/src/test/java/org/dataloader/stats/StatisticsTest.java
index b900807..6c90907 100644
--- a/src/test/java/org/dataloader/stats/StatisticsTest.java
+++ b/src/test/java/org/dataloader/stats/StatisticsTest.java
@@ -1,11 +1,11 @@
 package org.dataloader.stats;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.Map;
 
+import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertThat;
 
 public class StatisticsTest {
 

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