Add failing test for demonstration purpose

Author: gjbex

source-code/testing/Hypothesis/factorial.py

@@ -25,3 +25,22 @@ def fac(n: int) -> int:
     for i in range(n, 1, -1):
         result *= i
     return result
+
+
+def fac_bad(n: int) -> int:
+    '''Return the factorial of n
+
+    Parameters
+    ----------
+    n : int
+        The number to compute the factorial of
+
+    Returns
+    -------
+    int
+        The factorial of n
+    '''
+    result = 1
+    for i in range(n, 1, -1):
+        result *= i
+    return result

source-code/testing/Hypothesis/test_factorial.py

@@ -1,16 +1,31 @@
 from math import factorial as fac_math
 from hypothesis import assume, given, strategies as st
-from factorial import fac
+from factorial import fac, fac_bad
 
 
 @given(st.integers(min_value=0, max_value=100))
-def test_fac_same(n):
+def test_fac(n):
     assert fac(n) == fac_math(n)
 
 
 @given(st.integers(max_value=-1))
 def test_fac_neg(n):
     try:
-        assert fac(n) == fac_math(n)
+        _ = fac(n)
+        assert False, 'no ValueError raised'
+    except ValueError:
+        assert n < 0
+
+
+@given(st.integers(min_value=0, max_value=100))
+def test_fac_bad(n):
+    assert fac_bad(n) == fac_math(n)
+
+
+@given(st.integers(max_value=-1))
+def test_fac_bad_neg(n):
+    try:
+        _ = fac_bad(n)
+        assert False, 'no ValueError raised'
     except ValueError:
         assert n < 0