def test_xor() -> None:
    'Test ``Xor`` condition. '

    @argcomb(Xor('a', 'b', 'c'))
    def f(a: Any=None, b: Any=None, c: Any=None) -> None:
        ...
    f(a=1)
    f(b=1)
    f(c=1)
    with pytest.raises(InvalidArgumentCombination):
        f(a=1, b=1)
    with pytest.raises(InvalidArgumentCombination):
        f(a=1, c=1)
    with pytest.raises(InvalidArgumentCombination):
        f(b=1, c=1)
    with pytest.raises(InvalidArgumentCombination):
        f(a=1, b=1, c=1)
    with pytest.raises(InvalidArgumentCombination):
        f()
Test ``Xor`` condition.
def test_xor() -> None:
    ' '

    @argcomb(Xor('a', 'b', 'c'))
    def f(a: Any=None, b: Any=None, c: Any=None) -> None:
        ...
    f(a=1)
    f(b=1)
    f(c=1)
    with pytest.raises(InvalidArgumentCombination):
        f(a=1, b=1)
    with pytest.raises(InvalidArgumentCombination):
        f(a=1, c=1)
    with pytest.raises(InvalidArgumentCombination):
        f(b=1, c=1)
    with pytest.raises(InvalidArgumentCombination):
        f(a=1, b=1, c=1)
    with pytest.raises(InvalidArgumentCombination):
        f()