Re-run test in v23 is slower than v22 on Windows

[Isaddo]

💥 Regression Report

Re-run test in version 23 is significantly slower than version 22 on Windows

Last working version

Worked up to version: 22.4.4

Stopped working in version: 23.0.0

To Reproduce

repo: testjest22
repo: testjest23

These two repos only contains a test file jest.test.js and install different jest version.

test('foo', () => {
  expect('foo').toBe('foo')
})

run yarn test --watchAll --env=node

then, press Enter to trigger a test run
In v22, it takes about 0.05s, but over 2s in v23

When editing test file to trigger re-run,
v22 can finish in 0.5s but v23 usually takes close to 3s

Run npx envinfo --preset jest

  System:
    OS: Windows 10
    CPU: x64 Intel(R) Core(TM) i5-5250U CPU @ 1.60GHz
  Binaries:
    Yarn: 1.7.0 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
    npm: 5.6.0 - C:\Program Files\nodejs\npm.CMD

Update: It is an issue only on Windows, test it on Linux, just a little bit slower but acceptable.

[thymikee]

Anyone would like to help finding which commit might be responsible for the slowdown?

[ckwong90]

yes, I experienced this as well. Also console.log messages are not showing up consistently compared to v22. I suspect it is being overwritten by jest messages.

[lukeapage]

I can confirm the problem.. on this test suite,, though not as pronounced.

The problem seems to be down to startup ;- for me, on a large test suite I didn't notice a significant change.

Jest 23 - 1.6s (real 3.7s), 1.25s (real 3.074s), 1.24s (real 3.06s)
Jest 22 - 1.1s (real 3.0s), 0.52s (real 2.12s), 0.52s (real 2.12s)

[lukeapage]

I wasn't running in watch mode. with watch all after already warmed up

jest 23 - 0.5s pre-warmed first run, 0.8 after changing file
jest 22 - 1.8s pre-warmed first run, 2.3s after changing file

[gsteacy]

I did a bisect and it looks like the problem was introduced with a deps upgrade in d1ce3cd. The upgrade to micromatch was reverted later but it's still slow in master so it must be something else.

[thymikee]

Are you sure? Besides micromatch, the only deps that changed were dev ones

[gsteacy]

Actually I think there might be something else involved too. The deps upgrade definitely increased the watch mode runs on file change from ~0.46s to ~1-1.1s. However, reverting micromatch (e930c70) didn't resolve the problem. In fact it's actually slower than when micromatch was upgraded. I think some other change in between is contributing to the problem. I'll do another bisect to see if I can find it.

[gsteacy]

Ah, it looks like a significant contributor is 664681a. I don't think it's the only issue but it certainly hurts this particular repo, as it only has one test. There's overhead spinning up a worker. Reverting that commit on master brings it down from 2.5-3.3s to 0.7-0.8s. That's still more than 0.46s, but it's better. Not sure what the impact would be on a larger battery of tests.

[gsteacy]

I tested on a larger (but by no means large) codebase and found that a6aa304 decreased performance measurably on my machine as well.

• Watch: 21.2s
• Non-watch: 12.5s

For reference:

22.4.2

• Watch: 17.5s
• Non-watch: 11.2s

master

• Watch: 24.4s
• Non-watch: 14.6s

I haven't been able to determine what else is slowing down test runs between 22.4.2 and master. Performance goes up and down between the two revisions so it's hard to really find a cause. I don't think it's any single commit, but rather the cumulative effect of multiple changes.

[mpseidel]

Can confirm 23 is much slower than 22 on re-running tests on Windows using Typescript and ts-jest.

23.4.1 adds ~3 seconds to a 3ms noop test

22.4.4 runs test re-runs as fast as expected

[Lazarencjusz]

I confirm --watch problems on Windows using Typescript and ts-jest:
v23: >13s
v22: >8s
v21: >2s

 test('------1------', () => {
    expect(1).toEqual(1);
  });

[deerares]

It is actual for MacOS too "jest 23.4.2" is slower than "jest 22.1.4" at most 80%