[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/sqllab/ResultSet_spec.jsx

@@ -1,6 +1,5 @@
 import React from 'react';
 import { shallow } from 'enzyme';
-import { expect } from 'chai';
 import sinon from 'sinon';
 
 import { Alert, ProgressBar } from 'react-bootstrap';
@@ -41,11 +40,11 @@ describe('ResultSet', () => {
   };
 
   it('is valid', () => {
-    expect(React.isValidElement(<ResultSet {...mockedProps} />)).to.equal(true);
+    expect(React.isValidElement(<ResultSet {...mockedProps} />)).toBe(true);
   });
   it('renders a Table', () => {
     const wrapper = shallow(<ResultSet {...mockedProps} />);
-    expect(wrapper.find(FilterableTable)).to.have.length(1);
+    expect(wrapper.find(FilterableTable)).toHaveLength(1);
   });
   describe('componentWillReceiveProps', () => {
     const wrapper = shallow(<ResultSet {...mockedProps} />);
@@ -61,19 +60,19 @@ describe('ResultSet', () => {
     it('should update cached data', () => {
       wrapper.setProps(newProps);
 
-      expect(wrapper.state().data).to.deep.equal(newProps.query.results.data);
-      expect(clearQuerySpy.callCount).to.equal(1);
-      expect(clearQuerySpy.getCall(0).args[0]).to.deep.equal(newProps.query);
-      expect(fetchQuerySpy.callCount).to.equal(1);
-      expect(fetchQuerySpy.getCall(0).args[0]).to.deep.equal(newProps.query);
+      expect(wrapper.state().data).toEqual(newProps.query.results.data);
+      expect(clearQuerySpy.callCount).toBe(1);
+      expect(clearQuerySpy.getCall(0).args[0]).toEqual(newProps.query);
+      expect(fetchQuerySpy.callCount).toBe(1);
+      expect(fetchQuerySpy.getCall(0).args[0]).toEqual(newProps.query);
     });
   });
   describe('render', () => {
     it('should render success query', () => {
       const wrapper = shallow(<ResultSet {...mockedProps} />);
       const filterableTable = wrapper.find(FilterableTable);
-      expect(filterableTable.props().data).to.equal(mockedProps.query.results.data);
-      expect(wrapper.find(ExploreResultsButton)).to.have.length(1);
+      expect(filterableTable.props().data).toBe(mockedProps.query.results.data);
+      expect(wrapper.find(ExploreResultsButton)).toHaveLength(1);
     });
     it('should render empty results', () => {
       const wrapper = shallow(<ResultSet {...mockedProps} />);
@@ -83,9 +82,9 @@ describe('ResultSet', () => {
         },
       });
       wrapper.setProps({ query: emptyResults });
-      expect(wrapper.find(FilterableTable)).to.have.length(0);
-      expect(wrapper.find(Alert)).to.have.length(1);
-      expect(wrapper.find(Alert).shallow().text()).to.equal('The query returned no data');
+      expect(wrapper.find(FilterableTable)).toHaveLength(0);
+      expect(wrapper.find(Alert)).toHaveLength(1);
+      expect(wrapper.find(Alert).shallow().text()).toBe('The query returned no data');
     });
     it('should render cached query', () => {
       const wrapper = shallow(<ResultSet {...cachedQueryProps} />);
@@ -94,15 +93,15 @@ describe('ResultSet', () => {
       ];
       wrapper.setState({ data: cachedData });
       const filterableTable = wrapper.find(FilterableTable);
-      expect(filterableTable.props().data).to.equal(cachedData);
+      expect(filterableTable.props().data).toBe(cachedData);
     });
     it('should render stopped query', () => {
       const wrapper = shallow(<ResultSet {...stoppedQueryProps} />);
-      expect(wrapper.find(Alert)).to.have.length(1);
+      expect(wrapper.find(Alert)).toHaveLength(1);
     });
     it('should render running/pending/fetching query', () => {
       const wrapper = shallow(<ResultSet {...runningQueryProps} />);
-      expect(wrapper.find(ProgressBar)).to.have.length(1);
+      expect(wrapper.find(ProgressBar)).toHaveLength(1);
     });
   });
 });