Add tests on the problem level that show the infinite answer bug

common/lib/capa/capa/tests/test_responsetypes.py

@@ -438,6 +438,36 @@ class FormulaResponseTest(ResponseTest):
             self.assert_grade(problem, incorrect, 'incorrect',
                               msg="Failed on function {0}; the given, incorrect answer was {1} but graded 'correct'".format(func, incorrect))
 
+    def test_grade_infinity(self):
+        # This resolves a bug where a problem with relative tolerance would
+        # pass with any arbitrarily large student answer.
+
+        sample_dict = {'x' : (1,2)}
+
+        # Test problem
+        problem = self.build_problem(sample_dict=sample_dict,
+                                     num_samples=10,
+                                     tolerance="1%",
+                                     answer="x")
+        # Expect such a large answer to be marked incorrect
+        input_formula = "x*1e999"
+        self.assert_grade(problem, input_formula, "incorrect")
+
+    def test_grade_nan(self):
+        # attempt to produce a value which causes the student's answer to be
+        # evaluated to nan. See if this is resolved correctly.
+
+        sample_dict = {'x' : (1,2)}
+
+        # Test problem
+        problem = self.build_problem(sample_dict=sample_dict,
+                                     num_samples=10,
+                                     tolerance="1%",
+                                     answer="x")
+        # Expect an incorrect answer (+ nan) to be marked incorrect
+        input_formula = "10*x + 0*1e999" # right now this evaluates to 'nan' for a given x
+        self.assert_grade(problem, input_formula, "incorrect")
+
 
 class StringResponseTest(ResponseTest):
     from response_xml_factory import StringResponseXMLFactory
@@ -714,6 +744,28 @@ class NumericalResponseTest(ResponseTest):
         incorrect_responses = ["", "4.5", "3.5", "0"]
         self.assert_multiple_grade(problem, correct_responses, incorrect_responses)
 
+    def test_grade_infinity(self):
+        # This resolves a bug where a problem with relative tolerance would
+        # pass with any arbitrarily large student answer.
+        problem = self.build_problem(question_text="What is 2 + 2 approximately?",
+                                     explanation="The answer is 4",
+                                     answer=4,
+                                     tolerance="10%")
+        correct_responses = []
+        incorrect_responses = ["1e999"]
+        self.assert_multiple_grade(problem, correct_responses, incorrect_responses)
+
+    def test_grade_nan(self):
+        # attempt to produce a value which causes the student's answer to be
+        # evaluated to nan. See if this is resolved correctly.
+        problem = self.build_problem(question_text="What is 2 + 2 approximately?",
+                                     explanation="The answer is 4",
+                                     answer=4,
+                                     tolerance="10%")
+        correct_responses = []
+        incorrect_responses = ["0*1e999"] # right now this evaluates to 'nan' for a given x
+        self.assert_multiple_grade(problem, correct_responses, incorrect_responses)
+
     def test_grade_with_script(self):
         script_text = "computed_response = math.sqrt(4)"
         problem = self.build_problem(question_text="What is sqrt(4)?",