Support keywords or annotations in `parametrize`.

[coady]

Proposal to enhance parametrize with support for keyword params. This seems more pythonic than the zipped format, for simple params. Reference implementation (under a different name):

def params(**kwargs):
    if len(kwargs) == 1:
        return pytest.mark.parametrize(*kwargs.popitem())
    return pytest.mark.parametrize(','.join(kwargs), zip(*kwargs.values()))

An example from the docs:

@pytest.mark.parametrize("test_input,expected", [
    ("3+5", 8),
    ("2+4", 6),
])
def test_eval(test_input, expected):
    assert eval(test_input) == expected

becomes:

@params(test_input=["3+5", "2+4"], expected=[8, 6])
def test_eval(test_input, expected):
    assert eval(test_input) == expected

Relatedly, it also seems a perfect use case for Python 3 annotations:

def parametrized(func):
    return params(**func.__annotations__)(func)

@parametrized
def test_eval(test_input: ["3+5", "2+4"], expected: [8, 6]):
    assert eval(test_input) == expected

[RonnyPfannschmidt]

at first glance im strictly opposed to passing along data values this way as its much less comprehensible what elements belong together

in addition this looks confusingly similar to combinatoric parametrization

after all

@parametrize("test_input",  ["3+5", "2+4"])
@parameterize("expected", [8, 6])

would result in 4 tests instead of 2

[nicoddemus]

I'm not a very fan of increasing the ways to parametrize tests, I don't think it would make it easy on the users.

@coady you should consider making that into a plugin.

[coady]

Based on feedback, made this into a plugin: pytest-parametrized, and made it explicit on how to combine params.

@parametrized           # only one param allowed
@parametrized.zip       # zipped
@parametrized.product   # cartesian product

And I'll mention another use case for anyone looking for this feature: when the param values aren't literals to start. Enums are a good example:

@paremetrized.zip
def test(myenum=MyEnum, ...):

[nicoddemus]

Awesome @coady, thanks for sharing. After you release 1.0, please consider opening a PR adding a note about this plugin to the official parametrize docs. 👍