Huge increase in test time since upgraded to jest 24 and new preset

Hi there, we have a medium sized project with around 1600 tests.

We upgraded yesterday to jest 24 with new preset, with recommended migrations changes. We use jsdom 13 as stated in the migration guide.

Please note no change was made to our project. On the same machine, here are the speed reports. It was run with jest alone, and reported result is the second launch of jest command (to ensure no cache problem or something like that).

Before, under jest 23:

Test Suites: 11 skipped, 169 passed, 169 of 180 total
Tests:       82 skipped, 1671 passed, 1753 total
Snapshots:   0 total
Time:        19.142s

After upgrading to new preset 7.0.1 and jest 24:

Test Suites: 11 skipped, 169 passed, 169 of 180 total
Tests:       82 skipped, 1671 passed, 1753 total
Snapshots:   0 total
Time:        29.138s

Attempt with jest 24 and old 6.0.2 preset (no jsdom 13):

Test Suites: 11 skipped, 169 passed, 169 of 180 total
Tests:       82 skipped, 1671 passed, 1753 total
Snapshots:   0 total
Time:        25.061s

Please note it’s especially components which encounter that problem. Our most complete component went from 2s testing under jest 23 to more than 8 sec itself alone in jest 24/preset 7.0.2.

[Ludevik]

@blackholegalaxy tests in my project were super slow after upgrade too, but i enabled isolatedModules in ts-jest options and they were back to normal. See this link. It might help you, but it has its costs.

[blackholegalaxy]

In our case it didn’t change much. 2 seconds average on a 45s run basis. The fact is with jest 24+, we have like… 10 seconds where NOTHING happens. Then tests start normally. Even with test cache enabled.