def multiply(a, b):
    # This function multiplies two numbers and returns the result
    # if one of the numbers is zero, the result will be zero
    # if the number are both positive, the result will be positive
    # if the number are both negative, the result will be positive
    # the multiplication is done by invoking a primitive
    return a * b

# This code has a comment that explains what the function does.
# Instead of relying on this comment to understand the behavior of the code,
# we can write some unit tests that verify the behavior of the function.

def multiply(first_multiplier, second_multiplier):
    return first_multiplier * second_multiplier

class TestMultiply(unittest.TestCase):
    def test_multiply_both_possitive_outcome_is_possitive(self):
        result = multiply(2, 3)
        self.assertEqual(result, 6)
    def test_multiply_both_negative_outcome_is_positive(self):
        result = multiply(-2, -4)
        self.assertEqual(result, 8)
    def test_multiply_first_is_zero_outcome_is_zero(self):
        result = multiply(0, -4)
        self.assertEqual(result, 0)
    def test_multiply_second_is_zero_outcome_is_zero(self):
        result = multiply(3, 0)
        self.assertEqual(result, 0)
    def test_multiply_both_are_zero_outcome_is_zero(self):
        result = multiply(0, 0)
        self.assertEqual(result, 0)           

# We define a test function called test_multiply,
# which calls the multiply function with different arguments 
# and verifies that the result is correct using the assertEqual method.

# 1. Take the comment of the method explaining what the function does.
# 2. Rename the method with the comment description (the what).
# 3. Create tests to verify the comments. 
# 4. Omit irrelevant implementation details