testing.py

# def add_positive_numbers(x, y):
#     assert x > 0 and y > 0, "Both numbers must be positive!"
#     return x + y

# print(add_positive_numbers(1, 1)) # 2
# add_positive_numbers(1, -1) 

# def add(a, b):
#     """
#     >>> add(2, 3)
#     5
#     >>> add(100,200)
#     300
#     """
#     return a * b

def double(values):
    """double the values in a list

    >>> double([1,2,3,4])
    [2, 4, 6, 8]

    >>> double([])
    []

    >>> double(['a', 'b', 'c'])
    ['aa', 'bb', 'cc']

    >>> double([True, None])
    Traceback (most recent call last):
        ...
    TypeError: unsupported operand type(s) for *: 'int' and 'NoneType'
    """
    return [2 * element for element in values]