Speed up performance massively with --maxWorkers=1

[AlCalzone]

Issue :

This is not really an issue but rather a solution that could be mentioned in the docs.
I've been a bit annoyed with the performance of ts-jest. The VSCode jest plugin and watch mode were each taking 20-30s each run with the default config on a small-to-medium-sized project.

This is with the default 2 workers:

Test Suites: 1 skipped, 30 passed, 30 of 31 total
Tests:       8 skipped, 15 todo, 291 passed, 314 total
Snapshots:   0 total
Time:        24.353s
Ran all test suites.

Note: This is a computer with decent specs and 4 CPUs. I changed the command line to include --maxWorkers=1:

Test Suites: 1 skipped, 30 passed, 30 of 31 total
Tests:       8 skipped, 15 todo, 291 passed, 314 total
Snapshots:   0 total
Time:        3.325s, estimated 45s
Ran all test suites.

which is a massive performance improvement.

[ahnpnl]

PR is welcome for README 😀

[bbugh]

Wow, thank you for this, it is a massive improvement. I wonder what ts-jest is doing that causes this.

[ahnpnl]

#1049 is one of the issues I think, I don't know which else causes perf issues.

[kbrock84]

I ran into this issue as well.

Would you consider adding a Known Issues section to the README and include this?

I can submit a PR for this if needed, but Maybe we should wait until #1049 is merged to decide.

[ahnpnl]

I ran into this issue as well.

Would you consider adding a Known Issues section to the README and include this?

I can submit a PR for this if needed, but Maybe we should wait until #1049 is merged to decide.

#1049 is in master now. You can test it locally.

Besides, setting isolateModules to true also speeds up a lot

[ahnpnl]

close as superseded by #1115

[ahnpnl]

FYI: #1549 will be in alpha version of ts-jest (possibly today). Anyone who is using ts-jest please help to test the alpha version and give us some feedbacks for #1115