[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/dashboard/components/gridComponents/Tab_spec.jsx

@@ -1,7 +1,6 @@
 import { Provider } from 'react-redux';
 import React from 'react';
 import { mount } from 'enzyme';
-import { expect } from 'chai';
 import sinon from 'sinon';
 
 import DashboardComponent from '../../../../../src/dashboard/containers/DashboardComponent';
@@ -57,16 +56,14 @@ describe('Tabs', () => {
   describe('renderType=RENDER_TAB', () => {
     it('should render a DragDroppable', () => {
       const wrapper = setup();
-      expect(wrapper.find(DragDroppable)).to.have.length(1);
+      expect(wrapper.find(DragDroppable)).toHaveLength(1);
     });
 
     it('should render an EditableTitle with meta.text', () => {
       const wrapper = setup();
       const title = wrapper.find(EditableTitle);
-      expect(title).to.have.length(1);
-      expect(title.find('input').prop('value')).to.equal(
-        props.component.meta.text,
-      );
+      expect(title).toHaveLength(1);
+      expect(title.find('input').prop('value')).toBe(props.component.meta.text);
     });
 
     it('should call updateComponents when EditableTitle changes', () => {
@@ -74,25 +71,25 @@ describe('Tabs', () => {
       const wrapper = setup({ editMode: true, updateComponents });
       wrapper.find(EditableTitle).prop('onSaveTitle')('New title');
 
-      expect(updateComponents.callCount).to.equal(1);
-      expect(updateComponents.getCall(0).args[0].TAB_ID.meta.text).to.equal(
+      expect(updateComponents.callCount).toBe(1);
+      expect(updateComponents.getCall(0).args[0].TAB_ID.meta.text).toBe(
         'New title',
       );
     });
 
     it('should render a WithPopoverMenu', () => {
       const wrapper = setup();
-      expect(wrapper.find(WithPopoverMenu)).to.have.length(1);
+      expect(wrapper.find(WithPopoverMenu)).toHaveLength(1);
     });
 
     it('should render a DeleteComponentModal when focused if its not the only tab', () => {
       let wrapper = setup();
       wrapper.find(WithPopoverMenu).simulate('click'); // focus
-      expect(wrapper.find(DeleteComponentModal)).to.have.length(0);
+      expect(wrapper.find(DeleteComponentModal)).toHaveLength(0);
 
       wrapper = setup({ editMode: true });
       wrapper.find(WithPopoverMenu).simulate('click');
-      expect(wrapper.find(DeleteComponentModal)).to.have.length(1);
+      expect(wrapper.find(DeleteComponentModal)).toHaveLength(1);
 
       wrapper = setup({
         editMode: true,
@@ -102,7 +99,7 @@ describe('Tabs', () => {
         },
       });
       wrapper.find(WithPopoverMenu).simulate('click');
-      expect(wrapper.find(DeleteComponentModal)).to.have.length(0);
+      expect(wrapper.find(DeleteComponentModal)).toHaveLength(0);
     });
 
     it('should show modal when clicked delete icon', () => {
@@ -112,8 +109,8 @@ describe('Tabs', () => {
       wrapper.find('.icon-button').simulate('click');
 
       const modal = document.getElementsByClassName('modal');
-      expect(modal).to.have.length(1);
-      expect(deleteComponent.callCount).to.equal(0);
+      expect(modal).toHaveLength(1);
+      expect(deleteComponent.callCount).toBe(0);
     });
   });
 
@@ -121,7 +118,7 @@ describe('Tabs', () => {
     it('should render a DashboardComponent', () => {
       const wrapper = setup({ renderType: RENDER_TAB_CONTENT });
       // We expect 2 because this Tab has a Row child and the row has a Chart
-      expect(wrapper.find(DashboardComponent)).to.have.length(2);
+      expect(wrapper.find(DashboardComponent)).toHaveLength(2);
     });
   });
 });