code review

solutions/challenge_36/factorial.py

@@ -1,4 +1,4 @@
-"""this function allows to calculate the factorial of a non-negative integer n using recursive function"""
+"""factorial python module."""
 
 
 def factorial(n):
@@ -9,7 +9,19 @@ def factorial(n):
         n (int): Non-negative integer whose factorial is to be calculated.
 
     Returns:
-        int: Factorial of the input number n.
+        int: Factorial of the input number n. The return value must be greater than or equal to 1.
+
+    Raises:
+        ValueError: If n is a negative number.
+        Examples:
+        >>> factorial(0) # 0! = 1
+        1
+        >>> factorial(4) # 4! = 24
+        24
+        >>> factorial(-1)
+        Traceback (most recent call last):
+        ...
+        ValueError: Factorial is not defined for negative numbers.
     """
     if n < 0:
         raise ValueError("Factorial is not defined for negative numbers.")
@@ -19,6 +31,10 @@ def factorial(n):
 
 
 if __name__ == "__main__":
+    import doctest
+
+    print("running doctest...")
+    doctest.testmod(verbose=True)
     try:
         num = int(input("Enter a non-negative integer: "))
         print(f"Factorial of {num} is {factorial(num)}")

solutions/tests/challenge_36/test_factorial.py

@@ -1,4 +1,4 @@
-"""test the program factorial"""
+"""This unittest tests the python factorial program for positive numbers, negative numbers and zero"""
 
 import unittest
 from solutions.challenge_36.factorial import factorial
@@ -7,18 +7,15 @@
 class TestFactorial(unittest.TestCase):
     """test the program for positive numbers, negative numbers and zero"""
 
-    def test_factorial_positive(self):
-        """test the program for positive numbers"""
+    def test_factorial_with_positive(self):
+        """test factorial of 5."""
         self.assertEqual(factorial(5), 120)
-        self.assertEqual(factorial(4), 24)
-        self.assertEqual(factorial(3), 6)
-        self.assertEqual(factorial(1), 1)
 
-    def test_factorial_zero(self):
-        """test the program for zero"""
+    def test_factorial_with_zero(self):
+        """test factorial of 0"""
         self.assertEqual(factorial(0), 1)
 
-    def test_factorial_negative(self):
-        """test the program for negative numbers"""
+    def test_factorial_with_negative(self):
+        """test factorial of -1"""
         with self.assertRaises(ValueError):
             factorial(-1)