[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/modules/utils_spec.jsx

@@ -1,4 +1,3 @@
-import { expect, assert } from 'chai';
 import {
   formatSelectOptionsForRange,
   d3format,
@@ -10,83 +9,83 @@ import {
 
 describe('utils', () => {
   it('formatSelectOptionsForRange', () => {
-    expect(formatSelectOptionsForRange(0, 4)).to.deep.equal([
+    expect(formatSelectOptionsForRange(0, 4)).toEqual([
       [0, '0'],
       [1, '1'],
       [2, '2'],
       [3, '3'],
       [4, '4'],
     ]);
-    expect(formatSelectOptionsForRange(1, 2)).to.deep.equal([
+    expect(formatSelectOptionsForRange(1, 2)).toEqual([
       [1, '1'],
       [2, '2'],
     ]);
   });
   it('d3format', () => {
-    expect(d3format('.3s', 1234)).to.equal('1.23k');
-    expect(d3format('.3s', 1237)).to.equal('1.24k');
-    expect(d3format('', 1237)).to.equal('1.24k');
+    expect(d3format('.3s', 1234)).toBe('1.23k');
+    expect(d3format('.3s', 1237)).toBe('1.24k');
+    expect(d3format('', 1237)).toBe('1.24k');
   });
   describe('d3FormatPreset', () => {
     it('is a function', () => {
-      assert.isFunction(d3FormatPreset);
+      expect(typeof d3FormatPreset).toBe('function');
     });
     it('returns a working formatter', () => {
-      expect(d3FormatPreset('.3s')(3000000)).to.equal('3.00M');
+      expect(d3FormatPreset('.3s')(3000000)).toBe('3.00M');
     });
   });
   describe('d3TimeFormatPreset', () => {
     it('is a function', () => {
-      assert.isFunction(d3TimeFormatPreset);
+      expect(typeof d3TimeFormatPreset).toBe('function');
     });
     it('returns a working time formatter', () => {
-      expect(d3FormatPreset('smart_date')(0)).to.equal('1970');
+      expect(d3FormatPreset('smart_date')(0)).toBe('1970');
     });
   });
   describe('defaultNumberFormatter', () => {
-    expect(defaultNumberFormatter(10)).to.equal('10');
-    expect(defaultNumberFormatter(1)).to.equal('1');
-    expect(defaultNumberFormatter(1.0)).to.equal('1');
-    expect(defaultNumberFormatter(10.0)).to.equal('10');
-    expect(defaultNumberFormatter(10001)).to.equal('10.0k');
-    expect(defaultNumberFormatter(10100)).to.equal('10.1k');
-    expect(defaultNumberFormatter(111000000)).to.equal('111M');
-    expect(defaultNumberFormatter(0.23)).to.equal('230m');
+    expect(defaultNumberFormatter(10)).toBe('10');
+    expect(defaultNumberFormatter(1)).toBe('1');
+    expect(defaultNumberFormatter(1.0)).toBe('1');
+    expect(defaultNumberFormatter(10.0)).toBe('10');
+    expect(defaultNumberFormatter(10001)).toBe('10.0k');
+    expect(defaultNumberFormatter(10100)).toBe('10.1k');
+    expect(defaultNumberFormatter(111000000)).toBe('111M');
+    expect(defaultNumberFormatter(0.23)).toBe('230m');
 
-    expect(defaultNumberFormatter(-10)).to.equal('-10');
-    expect(defaultNumberFormatter(-1)).to.equal('-1');
-    expect(defaultNumberFormatter(-1.0)).to.equal('-1');
-    expect(defaultNumberFormatter(-10.0)).to.equal('-10');
-    expect(defaultNumberFormatter(-10001)).to.equal('-10.0k');
-    expect(defaultNumberFormatter(-10101)).to.equal('-10.1k');
-    expect(defaultNumberFormatter(-111000000)).to.equal('-111M');
-    expect(defaultNumberFormatter(-0.23)).to.equal('-230m');
+    expect(defaultNumberFormatter(-10)).toBe('-10');
+    expect(defaultNumberFormatter(-1)).toBe('-1');
+    expect(defaultNumberFormatter(-1.0)).toBe('-1');
+    expect(defaultNumberFormatter(-10.0)).toBe('-10');
+    expect(defaultNumberFormatter(-10001)).toBe('-10.0k');
+    expect(defaultNumberFormatter(-10101)).toBe('-10.1k');
+    expect(defaultNumberFormatter(-111000000)).toBe('-111M');
+    expect(defaultNumberFormatter(-0.23)).toBe('-230m');
   });
   describe('mainMetric', () => {
     it('is null when no options', () => {
-      expect(mainMetric([])).to.equal(undefined);
-      expect(mainMetric(null)).to.equal(undefined);
+      expect(mainMetric([])).toBeUndefined();
+      expect(mainMetric(null)).toBeUndefined();
     });
     it('prefers the "count" metric when first', () => {
       const metrics = [
         { metric_name: 'count' },
         { metric_name: 'foo' },
       ];
-      expect(mainMetric(metrics)).to.equal('count');
+      expect(mainMetric(metrics)).toBe('count');
     });
     it('prefers the "count" metric when not first', () => {
       const metrics = [
         { metric_name: 'foo' },
         { metric_name: 'count' },
       ];
-      expect(mainMetric(metrics)).to.equal('count');
+      expect(mainMetric(metrics)).toBe('count');
     });
     it('selects the first metric when "count" is not an option', () => {
       const metrics = [
         { metric_name: 'foo' },
         { metric_name: 'not_count' },
       ];
-      expect(mainMetric(metrics)).to.equal('foo');
+      expect(mainMetric(metrics)).toBe('foo');
     });
   });
 });