* [refactor] Migrate from Mocha+Chai to Jest
This change migrates all the existing unit tests
- to Jest's global expect and matchers from chai's imported expect, asserts and matchers.
- to Jest's describe/test from mocha's describe/it
The majority of the mechanical changes to tests are achieved through running jest-codemods. The only two note-worthy manual tweaks:
1. Setting a testURL of http://localhost in jest config and adjusting a few tests to leverage this value instead of relying on about:blank.
2. Re-enabling ExploreChartPanel_spec which was previously commented out as we cannot have empty tests with nothing in it with Jest. :)
This change also removes dependencies to Mocha and Chai.
* Remove the test:one command as it now does the same thing as test.
* Fixing lint errors. The diff looks large but is large done through `yarn run lint --fix`
The only noteworthy change is the one in eslintrc for tests. The env has been updated from mocha to jest.
* Adding eslint-plugin-jest and further modify tests.
- One small fix in sqllab's Timer Spec for a test that is not using the spy it created for testing.
- Deletion of a duplicated test caught by eslint-plugin-jest.
* - Make istanbul coverage work with Jest.
- Remove dependency on stand-alone istanbul and babel-istanbul as they're built-into jest. Yes!
* Attempt to fix dynamic imports in tests.
* run sequentially and log heap usage
* - tweaking maxworkers for travis and specifying coverageDirectory for codecov
- remove dynamic import in shim.js now that it is set in babelrc for tests only.
