feat(tests): Add unit-serial to test TASKGRAPH_SERIAL

[hneiva]

No description provided.

[bhearsum]

It looks like there's a test failure with TASKGRAPH_SERIAL currently? 😬. All the more reason to run these...

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.99%. Comparing base (320a2d5) to head (80eb1fb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #958      +/-   ##
==========================================
+ Coverage   77.72%   77.99%   +0.26%     
==========================================
  Files         130      130              
  Lines       12137    12140       +3     
  Branches     1477     1477              
==========================================
+ Hits         9434     9469      +35     
+ Misses       2315     2282      -33     
- Partials      388      389       +1     

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[hneiva]

Updated PR title + commit message to reflect changes

[bhearsum]

Approving, but please consider applying the suggestions.

[bhearsum]

Suggested change

	asynconly = pytest.mark.skipif(
	multiprocessonly = pytest.mark.skipif(

(async and multiprocess are not the same thing.)

[bhearsum]

Suggested change

	os.environ.get("TASKGRAPH_SERIAL"), reason="requires TASKGRAPH_SERIAL to be 0"
	os.environ.get("TASKGRAPH_SERIAL"), reason="requires multiprocessing to be enabled"

(This is checking whether or not TASKGRAPH_SERIAL is not at all, not looking for whether or not it is 0.)

[bhearsum]

I think it would be better to fix the threadsonly marker to account for TASKGRAPH_SERIAL rather than stack these in this case, but this works too.