[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/components/AdhocMetricEditPopover_spec.jsx

@@ -1,7 +1,6 @@
 /* eslint-disable no-unused-expressions */
 import React from 'react';
 import sinon from 'sinon';
-import { expect } from 'chai';
 import { shallow } from 'enzyme';
 import { Button, FormGroup, Popover } from 'react-bootstrap';
 
@@ -43,60 +42,60 @@ function setup(overrides) {
 describe('AdhocMetricEditPopover', () => {
   it('renders a popover with edit metric form contents', () => {
     const { wrapper } = setup();
-    expect(wrapper.find(Popover)).to.have.lengthOf(1);
-    expect(wrapper.find(FormGroup)).to.have.lengthOf(3);
-    expect(wrapper.find(Button)).to.have.lengthOf(2);
+    expect(wrapper.find(Popover)).toHaveLength(1);
+    expect(wrapper.find(FormGroup)).toHaveLength(3);
+    expect(wrapper.find(Button)).toHaveLength(2);
   });
 
   it('overwrites the adhocMetric in state with onColumnChange', () => {
     const { wrapper } = setup();
     wrapper.instance().onColumnChange(columns[0]);
-    expect(wrapper.state('adhocMetric')).to.deep.equal(sumValueAdhocMetric.duplicateWith({ column: columns[0] }));
+    expect(wrapper.state('adhocMetric')).toEqual(sumValueAdhocMetric.duplicateWith({ column: columns[0] }));
   });
 
   it('overwrites the adhocMetric in state with onAggregateChange', () => {
     const { wrapper } = setup();
     wrapper.instance().onAggregateChange({ aggregate: AGGREGATES.AVG });
-    expect(wrapper.state('adhocMetric')).to.deep.equal(sumValueAdhocMetric.duplicateWith({ aggregate: AGGREGATES.AVG }));
+    expect(wrapper.state('adhocMetric')).toEqual(sumValueAdhocMetric.duplicateWith({ aggregate: AGGREGATES.AVG }));
   });
 
   it('overwrites the adhocMetric in state with onSqlExpressionChange', () => {
     const { wrapper } = setup({ adhocMetric: sqlExpressionAdhocMetric });
     wrapper.instance().onSqlExpressionChange('COUNT(1)');
-    expect(wrapper.state('adhocMetric')).to.deep.equal(sqlExpressionAdhocMetric.duplicateWith({ sqlExpression: 'COUNT(1)' }));
+    expect(wrapper.state('adhocMetric')).toEqual(sqlExpressionAdhocMetric.duplicateWith({ sqlExpression: 'COUNT(1)' }));
   });
 
   it('overwrites the adhocMetric in state with onLabelChange', () => {
     const { wrapper } = setup();
     wrapper.instance().onLabelChange({ target: { value: 'new label' } });
-    expect(wrapper.state('adhocMetric').label).to.equal('new label');
-    expect(wrapper.state('adhocMetric').hasCustomLabel).to.be.true;
+    expect(wrapper.state('adhocMetric').label).toBe('new label');
+    expect(wrapper.state('adhocMetric').hasCustomLabel).toBe(true);
   });
 
   it('returns to default labels when the custom label is cleared', () => {
     const { wrapper } = setup();
     wrapper.instance().onLabelChange({ target: { value: 'new label' } });
     wrapper.instance().onLabelChange({ target: { value: '' } });
-    expect(wrapper.state('adhocMetric').label).to.equal('SUM(value)');
-    expect(wrapper.state('adhocMetric').hasCustomLabel).to.be.false;
+    expect(wrapper.state('adhocMetric').label).toBe('SUM(value)');
+    expect(wrapper.state('adhocMetric').hasCustomLabel).toBe(false);
   });
 
   it('prevents saving if no column or aggregate is chosen', () => {
     const { wrapper } = setup();
-    expect(wrapper.find(Button).find({ disabled: true })).to.have.lengthOf(0);
+    expect(wrapper.find(Button).find({ disabled: true })).toHaveLength(0);
     wrapper.instance().onColumnChange(null);
-    expect(wrapper.find(Button).find({ disabled: true })).to.have.lengthOf(1);
+    expect(wrapper.find(Button).find({ disabled: true })).toHaveLength(1);
     wrapper.instance().onColumnChange({ column: columns[0] });
-    expect(wrapper.find(Button).find({ disabled: true })).to.have.lengthOf(0);
+    expect(wrapper.find(Button).find({ disabled: true })).toHaveLength(0);
     wrapper.instance().onAggregateChange(null);
-    expect(wrapper.find(Button).find({ disabled: true })).to.have.lengthOf(1);
+    expect(wrapper.find(Button).find({ disabled: true })).toHaveLength(1);
   });
 
   it('highlights save if changes are present', () => {
     const { wrapper } = setup();
-    expect(wrapper.find(Button).find({ bsStyle: 'primary' })).to.have.lengthOf(0);
+    expect(wrapper.find(Button).find({ bsStyle: 'primary' })).toHaveLength(0);
     wrapper.instance().onColumnChange({ column: columns[1] });
-    expect(wrapper.find(Button).find({ bsStyle: 'primary' })).to.have.lengthOf(1);
+    expect(wrapper.find(Button).find({ bsStyle: 'primary' })).toHaveLength(1);
   });
 
   it('will initiate a drag when clicked', () => {
@@ -104,9 +103,9 @@ describe('AdhocMetricEditPopover', () => {
     wrapper.instance().onDragDown = sinon.spy();
     wrapper.instance().forceUpdate();
 
-    expect(wrapper.find('i.glyphicon-resize-full')).to.have.lengthOf(1);
-    expect(wrapper.instance().onDragDown.calledOnce).to.be.false;
+    expect(wrapper.find('i.glyphicon-resize-full')).toHaveLength(1);
+    expect(wrapper.instance().onDragDown.calledOnce).toBe(false);
     wrapper.find('i.glyphicon-resize-full').simulate('mouseDown');
-    expect(wrapper.instance().onDragDown.calledOnce).to.be.true;
+    expect(wrapper.instance().onDragDown.calledOnce).toBe(true);
   });
 });