Improve tests structure

[yangshun]

When jestjs/jest#5154 gets released, we should probably relook at our describe and test blocks. Some of them do not have a top level describe and phrasing is inconsistent across the various tests. This is a good chance to clean them up.

Proposed format:

• Top-level describe with the component name that you are testing for.
• For testing methods, use MyComponent.myMethod.

Feel free to add on to this. The purpose is to make them consistent across the code base.

[ZhangYiJiang]

This should be ready to be worked on, because Jest 22.0.5 has that PR, and we're using 22.3.0

[li-kai]

Leaving this here: https://www.npmjs.com/package/jest-codemods

[ZhangYiJiang]

Is that smart enough for our purpose? It seems like it's used for migrating tests from other frameworks to Jest

[ZhangYiJiang]

Just did a test and it seems that Flow libdef for Jest has not been updated to support this unfortunately. Let me see if I can make a PR for this.

[li-kai]

I just realized there is no need to write a codeshift to convert top level 'test' to 'describe'. We can just use regex.

[ZhangYiJiang]

PR opened on flow-typed - flow-typed/flow-typed#1858