[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/Markdown_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 AceEditor from 'react-ace';
 import ReactMarkdown from 'react-markdown';
@@ -51,27 +50,25 @@ describe('Markdown', () => {
 
   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 a WithPopoverMenu', () => {
     const wrapper = setup();
-    expect(wrapper.find(WithPopoverMenu)).to.have.length(1);
+    expect(wrapper.find(WithPopoverMenu)).toHaveLength(1);
   });
 
   it('should render a ResizableContainer', () => {
     const wrapper = setup();
-    expect(wrapper.find(ResizableContainer)).to.have.length(1);
+    expect(wrapper.find(ResizableContainer)).toHaveLength(1);
   });
 
   it('should only have an adjustableWidth if its parent is a Row', () => {
     let wrapper = setup();
-    expect(wrapper.find(ResizableContainer).prop('adjustableWidth')).to.equal(
-      true,
-    );
+    expect(wrapper.find(ResizableContainer).prop('adjustableWidth')).toBe(true);
 
     wrapper = setup({ ...props, parentComponent: mockLayout.present.CHART_ID });
-    expect(wrapper.find(ResizableContainer).prop('adjustableWidth')).to.equal(
+    expect(wrapper.find(ResizableContainer).prop('adjustableWidth')).toBe(
       false,
     );
   });
@@ -79,34 +76,34 @@ describe('Markdown', () => {
   it('should pass correct props to ResizableContainer', () => {
     const wrapper = setup();
     const resizableProps = wrapper.find(ResizableContainer).props();
-    expect(resizableProps.widthStep).to.equal(props.columnWidth);
-    expect(resizableProps.widthMultiple).to.equal(props.component.meta.width);
-    expect(resizableProps.heightMultiple).to.equal(props.component.meta.height);
-    expect(resizableProps.maxWidthMultiple).to.equal(
+    expect(resizableProps.widthStep).toBe(props.columnWidth);
+    expect(resizableProps.widthMultiple).toBe(props.component.meta.width);
+    expect(resizableProps.heightMultiple).toBe(props.component.meta.height);
+    expect(resizableProps.maxWidthMultiple).toBe(
       props.component.meta.width + props.availableColumnCount,
     );
   });
 
   it('should render an Markdown when NOT focused', () => {
     const wrapper = setup();
-    expect(wrapper.find(AceEditor)).to.have.length(0);
-    expect(wrapper.find(ReactMarkdown)).to.have.length(1);
+    expect(wrapper.find(AceEditor)).toHaveLength(0);
+    expect(wrapper.find(ReactMarkdown)).toHaveLength(1);
   });
 
   it('should render an AceEditor when focused and editMode=true and editorMode=edit', () => {
     const wrapper = setup({ editMode: true });
-    expect(wrapper.find(AceEditor)).to.have.length(0);
-    expect(wrapper.find(ReactMarkdown)).to.have.length(1);
+    expect(wrapper.find(AceEditor)).toHaveLength(0);
+    expect(wrapper.find(ReactMarkdown)).toHaveLength(1);
     wrapper.find(WithPopoverMenu).simulate('click'); // focus + edit
-    expect(wrapper.find(AceEditor)).to.have.length(1);
-    expect(wrapper.find(ReactMarkdown)).to.have.length(0);
+    expect(wrapper.find(AceEditor)).toHaveLength(1);
+    expect(wrapper.find(ReactMarkdown)).toHaveLength(0);
   });
 
   it('should render a ReactMarkdown when focused and editMode=true and editorMode=preview', () => {
     const wrapper = setup({ editMode: true });
     wrapper.find(WithPopoverMenu).simulate('click'); // focus + edit
-    expect(wrapper.find(AceEditor)).to.have.length(1);
-    expect(wrapper.find(ReactMarkdown)).to.have.length(0);
+    expect(wrapper.find(AceEditor)).toHaveLength(1);
+    expect(wrapper.find(ReactMarkdown)).toHaveLength(0);
 
     // we can't call setState on Markdown bc it's not the root component, so call
     // the mode dropdown onchange instead
@@ -114,8 +111,8 @@ describe('Markdown', () => {
     dropdown.prop('onChange')('preview');
     wrapper.update();
 
-    expect(wrapper.find(ReactMarkdown)).to.have.length(1);
-    expect(wrapper.find(AceEditor)).to.have.length(0);
+    expect(wrapper.find(ReactMarkdown)).toHaveLength(1);
+    expect(wrapper.find(AceEditor)).toHaveLength(0);
   });
 
   it('should call updateComponents when editMode changes from edit => preview, and there are markdownSource changes', () => {
@@ -127,7 +124,7 @@ describe('Markdown', () => {
     // the mode dropdown onchange instead
     const dropdown = wrapper.find(MarkdownModeDropdown);
     dropdown.prop('onChange')('preview');
-    expect(updateComponents.callCount).to.equal(0);
+    expect(updateComponents.callCount).toBe(0);
 
     dropdown.prop('onChange')('edit');
     // because we can't call setState on Markdown, change it through the editor
@@ -135,14 +132,14 @@ describe('Markdown', () => {
     const editor = wrapper.find(AceEditor);
     editor.prop('onChange')('new markdown!');
     dropdown.prop('onChange')('preview');
-    expect(updateComponents.callCount).to.equal(1);
+    expect(updateComponents.callCount).toBe(1);
   });
 
   it('should render a DeleteComponentButton when focused in editMode', () => {
     const wrapper = setup({ editMode: true });
     wrapper.find(WithPopoverMenu).simulate('click'); // focus
 
-    expect(wrapper.find(DeleteComponentButton)).to.have.length(1);
+    expect(wrapper.find(DeleteComponentButton)).toHaveLength(1);
   });
 
   it('should call deleteComponent when deleted', () => {
@@ -151,6 +148,6 @@ describe('Markdown', () => {
     wrapper.find(WithPopoverMenu).simulate('click'); // focus
     wrapper.find(DeleteComponentButton).simulate('click');
 
-    expect(deleteComponent.callCount).to.equal(1);
+    expect(deleteComponent.callCount).toBe(1);
   });
 });