Pytest: Add simplified way of creating "list of" fixtures

[adler-j]

I commonly find myself writing fixtures which are basically listings of some parameters:

@pytest.fixture(scope='module', params=[(64, 64), (64, 128), (128, 128)])
def shape(request):
    return request.param

I suggest that a function should be added that simplfies this. One example would be

shape = pytest.simple_fixture(params=[(64, 64), (64, 128), (128, 128)])

This would significantly reduce repetition in code, and is also much more readable in my opinion.

If you would be interested, I could make a PR with this.

[The-Compiler]

This sounds like you'd simply want to use @pytest.mark.parametrize, no?

[adler-j]

Well it is not strictly equivalent. Specifically pytest.mark.parametrize is not re-usable (in a trivial way) the same way fixtures are.

Basically what I suggest is:

shape = pytest.simple_fixture(params=[(64, 64), (128, 128)])

def test_something(shape):
    assert True

def test_something_else(shape):
    assert True

vs the current:

@pytest.mark.parametrize("shape", [(64, 64), (128, 128)])
def test_something(shape):
    assert True

@pytest.mark.parametrize("shape", [(64, 64), (128, 128)])
def test_something_else(shape):
    assert True

or without as much repetition:

parametrizer = pytest.mark.parametrize("shape", [(64, 64), (128, 128)])

@parametrizer
def test_something(shape):
    assert True

@parametrizer
def test_something_else(shape):
    assert True

I guess the improvement is somewhat minor, but it does save some lines, especially when you start needing several fixtures, or once you start writing fixtures that depend on fixtures.

[nicoddemus]

IMHO the last form is pretty good, all you need is a simple decorator applied to each test; I'm not sure it is worth adding a new function because of it.

Also I'm pretty sure you will need to pass in the name the fixture to make it work:

shape = pytest.simple_fixture("shape", params=[(64, 64), (128, 128)])

[nicoddemus]

If in the end we decide to not add this to the core, I would like to mention that the implementation is pretty simple and easy to make into a third-party plugin if the OP wants to:

def pytest_configure():
    import pytest
    pytest.simple_fixture = simple_fixture

def simple_fixture(name, params):
    @pytest.fixture(name=name, params=params)
    def inner(request):
        return request.param
    return inner

[The-Compiler]

FWIW I'm not really keen about having yet another way to do parametrization - from my experience giving pytest trainings and such, the difference between parametrizing tests and parametrizing fixtures is already confusing enough for newcomers.

[coady]

This is closely related to what I looking for in #2855, so I decided to support simple fixtures as well in pytest-parametrized.

shape = pytest.parametrized.fixture((64, 64), (128, 128))

[Zac-HD]

Closing this issue because there are adequate workarounds and an external implementation, so we don't need to make Pytest itself more complicated.