[refactor] Migrate from Mocha+Chai to Jest (#6079)

* [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.

superset/assets/spec/javascripts/utils/common_spec.jsx

@@ -1,52 +1,51 @@
-import { expect } from 'chai';
 import { isTruthy, optionFromValue } from '../../../src/utils/common';
 
 describe('utils/common', () => {
   describe('isTruthy', () => {
     it('evals false-looking strings properly', () => {
-      expect(isTruthy('f')).to.equal(false);
-      expect(isTruthy('false')).to.equal(false);
-      expect(isTruthy('no')).to.equal(false);
-      expect(isTruthy('n')).to.equal(false);
-      expect(isTruthy('F')).to.equal(false);
-      expect(isTruthy('False')).to.equal(false);
-      expect(isTruthy('NO')).to.equal(false);
-      expect(isTruthy('N')).to.equal(false);
+      expect(isTruthy('f')).toBe(false);
+      expect(isTruthy('false')).toBe(false);
+      expect(isTruthy('no')).toBe(false);
+      expect(isTruthy('n')).toBe(false);
+      expect(isTruthy('F')).toBe(false);
+      expect(isTruthy('False')).toBe(false);
+      expect(isTruthy('NO')).toBe(false);
+      expect(isTruthy('N')).toBe(false);
     });
     it('evals true-looking strings properly', () => {
-      expect(isTruthy('t')).to.equal(true);
-      expect(isTruthy('true')).to.equal(true);
-      expect(isTruthy('yes')).to.equal(true);
-      expect(isTruthy('y')).to.equal(true);
-      expect(isTruthy('Y')).to.equal(true);
-      expect(isTruthy('True')).to.equal(true);
-      expect(isTruthy('Yes')).to.equal(true);
-      expect(isTruthy('YES')).to.equal(true);
+      expect(isTruthy('t')).toBe(true);
+      expect(isTruthy('true')).toBe(true);
+      expect(isTruthy('yes')).toBe(true);
+      expect(isTruthy('y')).toBe(true);
+      expect(isTruthy('Y')).toBe(true);
+      expect(isTruthy('True')).toBe(true);
+      expect(isTruthy('Yes')).toBe(true);
+      expect(isTruthy('YES')).toBe(true);
     });
     it('evals bools properly', () => {
-      expect(isTruthy(false)).to.equal(false);
-      expect(isTruthy(true)).to.equal(true);
+      expect(isTruthy(false)).toBe(false);
+      expect(isTruthy(true)).toBe(true);
     });
     it('evals ints properly', () => {
-      expect(isTruthy(0)).to.equal(false);
-      expect(isTruthy(1)).to.equal(true);
+      expect(isTruthy(0)).toBe(false);
+      expect(isTruthy(1)).toBe(true);
     });
     it('evals constants properly', () => {
-      expect(isTruthy(null)).to.equal(false);
-      expect(isTruthy(undefined)).to.equal(false);
+      expect(isTruthy(null)).toBe(false);
+      expect(isTruthy(undefined)).toBe(false);
     });
     it('string auto is false', () => {
-      expect(isTruthy('false')).to.equal(false);
+      expect(isTruthy('false')).toBe(false);
     });
   });
   describe('optionFromValue', () => {
     it('converts values as expected', () => {
-      expect(optionFromValue(false)).to.deep.equal({ value: false, label: '<false>' });
-      expect(optionFromValue(true)).to.deep.equal({ value: true, label: '<true>' });
-      expect(optionFromValue(null)).to.deep.equal({ value: '<NULL>', label: '<NULL>' });
-      expect(optionFromValue('')).to.deep.equal({ value: '', label: '<empty string>' });
-      expect(optionFromValue('foo')).to.deep.equal({ value: 'foo', label: 'foo' });
-      expect(optionFromValue(5)).to.deep.equal({ value: 5, label: '5' });
+      expect(optionFromValue(false)).toEqual({ value: false, label: '<false>' });
+      expect(optionFromValue(true)).toEqual({ value: true, label: '<true>' });
+      expect(optionFromValue(null)).toEqual({ value: '<NULL>', label: '<NULL>' });
+      expect(optionFromValue('')).toEqual({ value: '', label: '<empty string>' });
+      expect(optionFromValue('foo')).toEqual({ value: 'foo', label: 'foo' });
+      expect(optionFromValue(5)).toEqual({ value: 5, label: '5' });
     });
   });
 });