Added more difficult example of factorial test

integration/test_factorial.py

@@ -12,6 +12,6 @@ class TestFactorial(unittest.TestCase):
 
     def factorial(self, mode):
         self.assertTrue(run_file(["factorial.alc", "primitives.alc"],
-            [1, 2, 3, 4],
-            [1, 2, 6, 24],
+            [1, 2, 3, 4, 20],
+            [1, 2, 6, 24, 2432902008176640000],
             mode))