v9 slowing down all tests

[Greg-Rose]

Hi, we recently updated our usage of this package to v9 (9.8.1 specifically) from a previous major version and have noticed that all of our frontend tests using jest and testing-library have significantly slowed down after this update.

All of the tests run multiple times (around 3-8 times) slower just from this package being updated to v9.0.0 and above. This is true not just for tests that include this component but all completely unrelated tests as well.

It seems to be just from the inclusion of this import: import { DayPicker } from "react-day-picker";. Without the import everything runs faster and with it everything runs slower.

Has anyone else encountered this? Any thoughts as why this might be happening or any direction to point me in to further investigate the cause?

[Greg-Rose]

For additional context, the slowness seems to occur with the new version when using the yarn node --experimental-vm-modules feature to run tests.

[gpbl]

Interesting. Could it be because the "type": "module" in package.json? 🤔

Would you mind to setup an environment or a repo to reproduce this case?