Assign process.env.JEST_RUN_IN_BAND value to check if testing is running serially.

[WeiAnAn]

Summary

Issue #9231.

I think use process.env.JEST_RUN_IN_BAND can solve this issue, and easier.

Test plan

Update TestScheduler tests, checking process.env.JEST_RUN_IN_BAND value.

[jeysal]

I'm wondering if we should just define JEST_WORKER_ID as 0 when running in band (it is 1-indexed in actual workers) to signal this (and documenting it)?
I feel like there was a discussion on this earlier this year but I can't find it. @thymikee @SimenB can you think of downsides to doing that instead?

[WeiAnAn]

@jeysal, it seems discuss in pr #5860.

[jeysal]

Thanks, awesome that you found it! I think casting the env variable string=>number=>boolean for a conditional as mentioned there is unlikely to happen and even if, it actually makes sense to me that the worker id is falsy if not running in a worker. So I'm in favor of changing JEST_WORKER_ID to 0 in the main process to signalize this.

[WeiAnAn]

I think if use JEST_WORKER_ID=0 to stand for running serially, it will cause a little confuse in code.

if (process.env.JEST_WORKER_ID == 0)
  // do something

It is hard to know what it mean in first time.

[SimenB]

All env variables are strings, so "0" wouldn't be falsy.

---

I still don't think this is the correct solution to the problem, and making tests behave differently depending on them running in band or not feels like an anti pattern

[WeiAnAn]

Or only set JEST_RUN_IN_BAND when running in band.
It would be undefined in multiple worker, and it is falsy.

[johncmunson]

making tests behave differently depending on them running in band or not feels like an anti pattern

@SimenB completely agree... this is most certainly an anti-pattern. However, this is javascript and sometimes other people's anti-patterns force you into writing an anti-pattern yourself just to compensate. It would be nice to have this escape hatch

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
Please note this issue tracker is not a help forum. We recommend using StackOverflow or our discord channel for questions.