Use react-testing-library

I would like to try out react-testing-library instead of using enzyme. In my experience it leads to more test coverage and more confidence while writing less code. The tests are also decoupled from the implementation that way.

If this is successful, I’d like to move all tests to react-testing-library and get rid of enzyme completely.

Additionally, our current tests are extremely slow in CI, some taking almost a minute.

 PASS   test  src/components/buttons/link-button/link-button.spec.js (52.084s)
 PASS   test  src/components/typography/text/text.spec.js (52.227s)
 PASS   test  src/components/inputs/number-input/number-input.spec.js (45.348s)
 PASS   test  src/components/switches/toggle/toggle-switch.spec.js (51.875s)
 PASS   test  src/utils/localized.spec.js (51.361s)
 PASS   test  src/components/buttons/ghost-button/ghost-button.spec.js (54.128s)
 PASS   test  src/components/buttons/accessible-button/accessible-button.spec.js (52.417s)

Source: https://travis-ci.org/commercetools/ui-kit/builds/424350666.

This might improve with react-testing-library as well.

[dferber90]

Done ✅

[dferber90]

Sure! I debugged the slowdown-over-time before and found that there is a memory leak somewhere in our setup, but I couldn’t get to the bottom of it. That’s why I have some hopes, that we could avoid the memory leak in case we get rid of enzyme and the related components. Now that you mention it though, the maxWorkers issue seems to be the cause of the slowdown observed here.