[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/explore/utils_spec.jsx

@@ -1,4 +1,3 @@
-import { expect } from 'chai';
 import URI from 'urijs';
 import { getExploreUrlAndPayload, getExploreLongUrl } from '../../../src/explore/exploreUtils';
 
@@ -9,14 +8,14 @@ describe('exploreUtils', () => {
   };
   const sFormData = JSON.stringify(formData);
   function compareURI(uri1, uri2) {
-    expect(uri1.toString()).to.equal(uri2.toString());
+    expect(uri1.toString()).toBe(uri2.toString());
   }
 
   describe('getExploreUrlAndPayload', () => {
     it('generates proper base url', () => {
       // This assertion is to show clearly the value of location.href
       // in the context of unit tests.
-      expect(location.href).to.equal('about:blank');
+      expect(location.href).toBe('http://localhost/');
 
       const { url, payload } = getExploreUrlAndPayload({
         formData,
@@ -28,7 +27,7 @@ describe('exploreUtils', () => {
         URI(url),
         URI('/superset/explore/'),
       );
-      expect(payload).to.deep.equals(formData);
+      expect(payload).toEqual(formData);
     });
     it('generates proper json url', () => {
       const { url, payload } = getExploreUrlAndPayload({
@@ -41,7 +40,7 @@ describe('exploreUtils', () => {
         URI(url),
         URI('/superset/explore_json/'),
       );
-      expect(payload).to.deep.equals(formData);
+      expect(payload).toEqual(formData);
     });
     it('generates proper json forced url', () => {
       const { url, payload } = getExploreUrlAndPayload({
@@ -55,7 +54,7 @@ describe('exploreUtils', () => {
         URI('/superset/explore_json/')
           .search({ force: 'true' }),
       );
-      expect(payload).to.deep.equals(formData);
+      expect(payload).toEqual(formData);
     });
     it('generates proper csv URL', () => {
       const { url, payload } = getExploreUrlAndPayload({
@@ -69,7 +68,7 @@ describe('exploreUtils', () => {
         URI('/superset/explore_json/')
           .search({ csv: 'true' }),
       );
-      expect(payload).to.deep.equals(formData);
+      expect(payload).toEqual(formData);
     });
     it('generates proper standalone URL', () => {
       const { url, payload } = getExploreUrlAndPayload({
@@ -83,7 +82,7 @@ describe('exploreUtils', () => {
         URI('/superset/explore/')
           .search({ standalone: 'true' }),
       );
-      expect(payload).to.deep.equals(formData);
+      expect(payload).toEqual(formData);
     });
     it('preserves main URLs params', () => {
       const { url, payload } = getExploreUrlAndPayload({
@@ -97,7 +96,7 @@ describe('exploreUtils', () => {
         URI('/superset/explore_json/')
           .search({ foo: 'bar' }),
       );
-      expect(payload).to.deep.equals(formData);
+      expect(payload).toEqual(formData);
     });
     it('generate proper save slice url', () => {
       const { url, payload } = getExploreUrlAndPayload({
@@ -111,7 +110,7 @@ describe('exploreUtils', () => {
         URI('/superset/explore_json/')
           .search({ foo: 'bar' }),
       );
-      expect(payload).to.deep.equals(formData);
+      expect(payload).toEqual(formData);
     });
     it('generate proper saveas slice url', () => {
       const { url, payload } = getExploreUrlAndPayload({
@@ -125,7 +124,7 @@ describe('exploreUtils', () => {
         URI('/superset/explore_json/')
           .search({ foo: 'bar' }),
       );
-      expect(payload).to.deep.equals(formData);
+      expect(payload).toEqual(formData);
     });
   });