[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/SliceAdder_spec.jsx

@@ -1,7 +1,6 @@
 import React from 'react';
 import { shallow } from 'enzyme';
 import sinon from 'sinon';
-import { expect } from 'chai';
 
 import { List } from 'react-virtualized';
 
@@ -40,7 +39,7 @@ describe('SliceAdder', () => {
           }
           return currentTimestamp < sortedTimestamps[index - 1];
         }),
-      ).to.equal(true);
+      ).toBe(true);
     });
 
     it('should sort by slice_name', () => {
@@ -50,20 +49,20 @@ describe('SliceAdder', () => {
       const expectedNames = Object.values(props.slices)
         .map(slice => slice.slice_name)
         .sort();
-      expect(sortedNames).to.deep.equal(expectedNames);
+      expect(sortedNames).toEqual(expectedNames);
     });
   });
 
   it('render List', () => {
     const wrapper = shallow(<SliceAdder {...props} />);
     wrapper.setState({ filteredSlices: Object.values(props.slices) });
-    expect(wrapper.find(List)).to.have.length(1);
+    expect(wrapper.find(List)).toHaveLength(1);
   });
 
   it('render error', () => {
     const wrapper = shallow(<SliceAdder {...errorProps} />);
     wrapper.setState({ filteredSlices: Object.values(props.slices) });
-    expect(wrapper.text()).to.have.string(errorProps.errorMessage);
+    expect(wrapper.text()).toContain(errorProps.errorMessage);
   });
 
   it('componentDidMount', () => {
@@ -73,8 +72,8 @@ describe('SliceAdder', () => {
     shallow(<SliceAdder {...props} />, {
       lifecycleExperimental: true,
     });
-    expect(SliceAdder.prototype.componentDidMount.calledOnce).to.equal(true);
-    expect(props.fetchAllSlices.calledOnce).to.equal(true);
+    expect(SliceAdder.prototype.componentDidMount.calledOnce).toBe(true);
+    expect(props.fetchAllSlices.calledOnce).toBe(true);
 
     SliceAdder.prototype.componentDidMount.restore();
     props.fetchAllSlices.restore();
@@ -96,12 +95,12 @@ describe('SliceAdder', () => {
         ...props,
         lastUpdated: new Date().getTime(),
       });
-      expect(wrapper.instance().setState.calledOnce).to.equal(true);
+      expect(wrapper.instance().setState.calledOnce).toBe(true);
 
       const stateKeys = Object.keys(
         wrapper.instance().setState.lastCall.args[0],
       );
-      expect(stateKeys).to.include('filteredSlices');
+      expect(stateKeys).toContain('filteredSlices');
     });
 
     it('select slices should update state', () => {
@@ -109,12 +108,12 @@ describe('SliceAdder', () => {
         ...props,
         selectedSliceIds: [127],
       });
-      expect(wrapper.instance().setState.calledOnce).to.equal(true);
+      expect(wrapper.instance().setState.calledOnce).toBe(true);
 
       const stateKeys = Object.keys(
         wrapper.instance().setState.lastCall.args[0],
       );
-      expect(stateKeys).to.include('selectedSliceIdsSet');
+      expect(stateKeys).toContain('selectedSliceIdsSet');
     });
   });
 
@@ -133,21 +132,21 @@ describe('SliceAdder', () => {
     it('searchUpdated', () => {
       const newSearchTerm = 'new search term';
       wrapper.instance().searchUpdated(newSearchTerm);
-      expect(spy.calledOnce).to.equal(true);
-      expect(spy.lastCall.args[0]).to.equal(newSearchTerm);
+      expect(spy.calledOnce).toBe(true);
+      expect(spy.lastCall.args[0]).toBe(newSearchTerm);
     });
 
     it('handleSelect', () => {
       const newSortBy = 1;
       wrapper.instance().handleSelect(newSortBy);
-      expect(spy.calledOnce).to.equal(true);
-      expect(spy.lastCall.args[1]).to.equal(newSortBy);
+      expect(spy.calledOnce).toBe(true);
+      expect(spy.lastCall.args[1]).toBe(newSortBy);
     });
 
     it('handleKeyPress', () => {
       wrapper.instance().handleKeyPress(mockEvent);
-      expect(spy.calledOnce).to.equal(true);
-      expect(spy.lastCall.args[0]).to.equal(mockEvent.target.value);
+      expect(spy.calledOnce).toBe(true);
+      expect(spy.lastCall.args[0]).toBe(mockEvent.target.value);
     });
   });
 });