def multiply(a, b):
    return a * b

def divide(a, b):
    if b == 0:
        raise ValueError("Division by zero is not allowed")
    return a / b

if __name__ == "__main__":
    # Test multiply
    assert multiply(2, 3) == 6
    assert multiply(-1, 5) == -5

    # Test divide
    assert divide(6, 3) == 2
    assert divide(5, 2) == 2.5

    # Test division by zero
    try:
        divide(1, 0)
    except ValueError as e:
        assert str(e) == "Division by zero is not allowed"
    else:
        assert False, "Expected ValueError for division by zero"

    print("All tests passed!")