Create new dist option 'loadgroup'

[baekdohyeop]

Checklist

• Make sure to include reasonable tests for your change if necessary
• Add change log

Intro

There are currently several options for distributing tests,
but there is still no suitable option for the following cases:

Case 1

In this case, it is efficient to divide all tests into different sessions.

@pytest.mark.parametrize('param', [A, B, C, D])
def test_something_heavy(param):
    do_something_heavy_test

Case 2

In this case, it is efficient to run all tests in the same session.

def test_something_light_1(heavy_fixture_cannot_filelock):
    do_something_light_test

def test_something_light_2(heavy_fixture_cannot_filelock):
    do_something_light_test

def test_something_light_3(heavy_fixture_cannot_filelock):
    do_something_light_test

Limit

If you use the loadscope option, all tests in Case 1 are performed in same session,
If the load option is used, all tests of Case 2 may be performed in different sessions.

Suggestion

Use the following xgroup mark and specify the name through the parameter.
Then, tests with the same name are executed in the same session.

@pytest.mark.xgroup(name="same_session")
def test_something_light_1(heavy_fixture_cannot_filelock):
    do_something_light_test

@pytest.mark.xgroup(name="same_session")
def test_something_light_2(heavy_fixture_cannot_filelock):
    do_something_light_test

@pytest.mark.xgroup(name="same_session")
def test_something_light_3(heavy_fixture_cannot_filelock):
    do_something_light_test

[nicoddemus]

Thanks a lot @baekdohyeop for following up with this!

Left a few comments, please take a look.

Besides, could you please add a description of the new option to the README? Probably showing some code would be helpful there too.

[nicoddemus]

👍

[baekdohyeop]

@nicoddemus
I'm not good at English, so I'd appreciate it if you could improve it.
Thank you.

[nicoddemus]

I'm not good at English, so I'd appreciate it if you could improve it.

Your English is very good, don't worry about it. 😁

I'm merging as is, and plan to give a quick overhaul of the README in a separate PR. Thanks!

[baekdohyeop]

Thanks!