build: parallelize slow tests

[DevanceJ]

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Summarize your changes:
Fixes #3255
After referring to https://circleci.com/docs/parallelism-faster-jobs/ I increased parallel execution environments to 4 and also set timings type to classname

[yangannyx]

This is super cool! Awesome seeing the four buckets in the CI run here.

What exactly are classnames referring to in a typical forge test? I'm curious because I see that the time taken between the 4 buckets seems rather uneven, and I'm concerned Circle CI isn't optimizing from past runs properly

[DevanceJ]

The documentation says that --split-by=timings should out of the box split the tests evenly across all the executors but when I tested it on my personal circleci setup for my forked repository I noticed the tests weren't split evenly, that's why I was trying to use --timings-type to maybe get it working appropriately. I'll go through the docs more thoroughly and do some digging around this and let you know what I find.

[yangannyx]

Yeah, reading the docs I agree we should use --split-by=timings and --timings-type. I'm wondering if Circle isn't able to identify classnames on our tests, which is leading to the uneven distribution. Have you tried setting --timings-type to name or file and seeing if that makes things more even?

[DevanceJ]

Hi sorry for the delay. Looking into this now. --timings-type=file is default behaviour which I think we should use for our tests.

[DevanceJ]

Currently we only use parallelism for slow-tests which is fine but slow-tests-x64-node/windows take up the maximum time, should I try using 8 nodes.

[yangannyx]

Hm, I don't think file is a great choice to split tests on either - we only have 6 slow test files to begin with, one which only runs on Linux. I also suspect that the tests that take the longest are located within the same files and not across files (see the electron-forge API tests in api_spec_slow.ts).

That being said, the goal here is to get an even distribution of tests by duration across each parallel bucket. Looking at the most recent CI run on this PR, I'm still seeing one bucket that takes the most time. I would maybe try measuring how long tests within the *_spec_slow.ts files are taking and seeing if --timings-type=name produces a more even distribution

[DevanceJ]

Hi so I looked into the tests more deeply and learned that the Windows slow tests are taking most of the time to complete the installation of node modules and to configure wixtoolset, and for some reason CircleCi is not able to split the slow tests the way it should.

Yes you are right using --timings-type=name could be a possible solution to the optimisation of slow tests.

[DevanceJ]

Looks like this documentation is not appropriate for our configuration because according to the current test failure and this.
Available values for --timings-type are filename, classname, testname, autodetect
I think using testname could be appropriate.

[erickzhao]

Going to put this into draft mode until #3585 is resolved

[yangannyx]

This PR should be unblocked by #3620 @DevanceJ! Apologies for the delay 🙇