aimacode · norvig · Oct 19, 2017 · Oct 1, 2017 · Oct 1, 2017 · Oct 1, 2017
diff --git a/learning.py b/learning.py
@@ -984,8 +984,8 @@ def flatten(seqs): return sum(seqs, [])
 
 
 def err_ratio(predict, dataset, examples=None, verbose=0):
-    """Return the proportion of the examples that are NOT correctly predicted."""
-    """verbose - 0: No output; 1: Output wrong; 2 (or greater): Output correct"""
+    """Return the proportion of the examples that are NOT correctly predicted.
+    verbose - 0: No output; 1: Output wrong; 2 (or greater): Output correct"""
     if examples is None:
         examples = dataset.examples
     if len(examples) == 0:

diff --git a/tests/test_csp.py b/tests/test_csp.py
@@ -1,5 +1,10 @@
 import pytest
+from utils import failure_test
 from csp import *
+import random
+
+
+random.seed("aima-python")
 
 
 def test_csp_assign():
@@ -331,10 +336,12 @@ def test_backtracking_search():
 
 
 def test_min_conflicts():
-    random.seed("aima-python")
     assert min_conflicts(australia)
-    assert min_conflicts(usa)
     assert min_conflicts(france)
+
+    tests = [(usa, None)] * 3
+    assert failure_test(min_conflicts, tests) > 1/3
+
     australia_impossible = MapColoringCSP(list('RG'), 'SA: WA NT Q NSW V; NT: WA Q; NSW: Q V; T: ')
     assert min_conflicts(australia_impossible, 1000) is None
 
@@ -351,7 +358,7 @@ def test_parse_neighbours():
 def test_topological_sort():
     root = 'NT'
     Sort, Parents = topological_sort(australia,root)
-    
+
     assert Sort == ['NT','SA','Q','NSW','V','WA']
     assert Parents['NT'] == None
     assert Parents['SA'] == 'NT'

diff --git a/tests/test_learning.py b/tests/test_learning.py
@@ -168,9 +168,13 @@ def test_decision_tree_learner():
 def test_random_forest():
     iris = DataSet(name="iris")
     rF = RandomForest(iris)
-    assert rF([5, 3, 1, 0.1]) == "setosa"
-    assert rF([6, 5, 3, 1]) == "versicolor"
-    assert rF([7.5, 4, 6, 2]) == "virginica"
+    tests = [([5.0, 3.0, 1.0, 0.1], "setosa"),
+             ([5.1, 3.3, 1.1, 0.1], "setosa"),
+             ([6.0, 5.0, 3.0, 1.0], "versicolor"),
+             ([6.1, 2.2, 3.5, 1.0], "versicolor"),
+             ([7.5, 4.1, 6.2, 2.3], "virginica"),
+             ([7.3, 3.7, 6.1, 2.5], "virginica")]
+    assert grade_learner(rF, tests) >= 1/3
 
 
 def test_neural_network_learner():

diff --git a/utils.py b/utils.py
@@ -416,6 +416,16 @@ def open_data(name, mode='r'):
     return open(aima_file)
 
 
+def failure_test(algorithm, tests):
+    """Grades the given algorithm based on how many tests it passes.
+    Most algorithms have arbitary output on correct execution, which is difficult
+    to check for correctness. On the other hand, a lot of algorithms output something
+    particular on fail (for example, False, or None).
+    tests is a list with each element in the form: (values, failure_output)."""
+    from statistics import mean
+    return mean(int(algorithm(x) != y) for x, y in tests)
+
+
 # ______________________________________________________________________________
 # Expressions