[UI] Consider migrating from enzyme to @testing-library/react

[Bobgy]

Part of #2407

This is an issue collector for problems we meet when using enzyme:

• Different behavior of setState comparing to react: setState is called synchronously from event handler enzymejs/enzyme#1608
  I got one test failing because of the nuance difference of setState behavior in tests. This is very frustrating because code runs well in a real app, but it breaks in tests. (turned out this was not the actual cause)
• Shallow rendering doesn't work with new context API: Complete React 16 support enzymejs/enzyme#1553

/area engprod
/area frontend

[Bobgy]

Currently marking as p2.
/priority p2

[Bobgy]

In #2676, I have installed react-testing-library, will continue to write new tests with it.

I'll consider migrating existing tests when there's such a need.
/close

[k8s-ci-robot]

@Bobgy: Closing this issue.

In response to this:

In #2676, I have installed react-testing-library, will continue to write new tests with it.

I'll consider migrating existing tests when there's such a need.
/close

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