Fix test functions for Prolog problems

Old version would return wrong values for programs with syntax errors.

1 files changed, 8 insertions, 10 deletions

diff --git a/prolog/problems/lists/len_2/common.py b/prolog/problems/lists/len_2/common.py
index 6737f33..d30588c 100644
--- a/prolog/problems/lists/len_2/common.py
+++ b/prolog/problems/lists/len_2/common.py
@@ -29,19 +29,17 @@ def test(program, solved_problems):
     code = (program + '\n' +
             server.problems.solutions_for_problems('prolog', solved_problems))
 
+    n_correct = 0
     engine_id = None
     try:
         engine_id, output = prolog.engine.create(code=code, timeout=1.0)
-        if not engine_id or 'error' in map(itemgetter(0), output):
-            # Engine creation failed, or syntax error in code.
-            return 0, len(test_cases)
-
-        n_correct = 0
-        for query, answers in test_cases:
-            # Limit inferences for each solution to curb unbounded recursion.
-            limited = 'call_with_inference_limit(({}), 100000, _)'.format(query)
-            if prolog.engine.check_answers(engine_id, query=limited, answers=answers, timeout=1.0):
-                n_correct += 1
+        if engine_id is not None and 'error' not in map(itemgetter(0), output):
+            # Engine successfully created, and no syntax error in program.
+            for query, answers in test_cases:
+                # Limit inferences for each solution to curb unbounded recursion.
+                limited = 'call_with_inference_limit(({}), 100000, _)'.format(query)
+                if prolog.engine.check_answers(engine_id, query=limited, answers=answers, timeout=1.0):
+                    n_correct += 1
     finally:
         if engine_id:
             prolog.engine.destroy(engine_id)