TST: Sort test parametrization in cosmology

[jdavies-st]

Description

This PR fixes an issue where test parametrizations in the cosmology subpackage were passed as sets, which are inherently unsorted. They need to be sorted if one is to use pytest-xdist. This converts them to sorted lists, as is done elsewhere in Astropy.

Fixes #16190

[github-actions]

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[pllim]

Why not just have _FLRW_redshift_methods be a list in the first place by applying the sort here?

astropy/astropy/cosmology/tests/helper.py

Line 78 in 9ebf44a

return methods

[jdavies-st]

I initially tried that, but the generated set is modified in a number of tests where redshift methods are removed. See the rest of the diff.

Turning the resulting set into a sorted list was the simplest solution, and it is done elsewhere in the code base. For example, here:

astropy/astropy/timeseries/periodograms/lombscargle/tests/test_statistics.py

Line 119 in a3cd9a9

@pytest.mark.parametrize("method", sorted(set(METHODS) - {"bootstrap"}))

[pllim]

I agree that maybe these tests are a little over-engineered but that is neither here nor there. Let's get this in as-is then. Really appreciate your help. Thanks!

[pllim]

I will see if auto-backport works. If not, then we will just not backport it.

[neutrinoceros]

very nice, thanks for getting to the bottom of this !