gh-1147: Create xp_no_jax

[connoraird]

Description

Add xp_no_jax to replace xpb when used as xp excluding JAX

Closes: #1147

Checks

• Is your code passing linting?
• Is your code passing tests?
• Have you added additional tests (if required)?
• Have you modified/extended the documentation (if required)?
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[ntessore]

Isn't this much cleaner handled by a skip at test level instead of changing the fixture?

[paddyroddy]

Looks good to me, not sure about the name though

[paddyroddy]

Isn't this much cleaner handled by a skip at test level instead of changing the fixture?

I think if we're not careful then that would skip the whole test. We're interested in skipping for certain backends, but still running the test. Could be done in another way potentially though.

[ntessore]

Isn't this much cleaner handled by a skip at test level instead of changing the fixture?

I think if we're not careful then that would skip the whole test. We're interested in skipping for certain backends, but still running the test. Could be done in another way potentially though.

We use this fixture in exactly one test. So we could just do:

def test_cls2cov_no_jax(xpb: ModuleType) -> None:
    if xpb.__name__ == "jax.numpy":
        pytest.skip("test does not work with jax")

    ...

[paddyroddy]

Ah, yes that makes sense. I was thinking of a more complex example modifying xp fixture itself.