[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/util/getDropPosition_spec.js

@@ -1,5 +1,3 @@
-import { expect } from 'chai';
-
 import getDropPosition, {
   DROP_TOP,
   DROP_RIGHT,
@@ -73,7 +71,7 @@ describe('getDropPosition', () => {
           draggingType: TAB_TYPE,
         }),
       );
-      expect(result).to.equal(null);
+      expect(result).toBeNull();
     });
   });
 
@@ -87,7 +85,7 @@ describe('getDropPosition', () => {
           draggingType: HEADER_TYPE,
         }),
       );
-      expect(result).to.equal(DROP_LEFT);
+      expect(result).toBe(DROP_LEFT);
     });
 
     it('should return DROP_RIGHT if component HAS children, and orientation is "row"', () => {
@@ -99,7 +97,7 @@ describe('getDropPosition', () => {
           hasChildren: true,
         }),
       );
-      expect(result).to.equal(DROP_RIGHT);
+      expect(result).toBe(DROP_RIGHT);
     });
 
     it('should return DROP_TOP if component has NO children, and orientation is "column"', () => {
@@ -111,7 +109,7 @@ describe('getDropPosition', () => {
           orientation: 'column',
         }),
       );
-      expect(result).to.equal(DROP_TOP);
+      expect(result).toBe(DROP_TOP);
     });
 
     it('should return DROP_BOTTOM if component HAS children, and orientation is "column"', () => {
@@ -124,7 +122,7 @@ describe('getDropPosition', () => {
           hasChildren: true,
         }),
       );
-      expect(result).to.equal(DROP_BOTTOM);
+      expect(result).toBe(DROP_BOTTOM);
     });
   });
 
@@ -143,7 +141,7 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(result).to.equal(DROP_TOP);
+      expect(result).toBe(DROP_TOP);
     });
 
     it('should return DROP_BOTTOM if orientation="row" and clientOffset is closer to component bottom than top', () => {
@@ -159,7 +157,7 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(result).to.equal(DROP_BOTTOM);
+      expect(result).toBe(DROP_BOTTOM);
     });
 
     it('should return DROP_LEFT if orientation="column" and clientOffset is closer to component left than right', () => {
@@ -176,7 +174,7 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(result).to.equal(DROP_LEFT);
+      expect(result).toBe(DROP_LEFT);
     });
 
     it('should return DROP_RIGHT if orientation="column" and clientOffset is closer to component right than left', () => {
@@ -193,7 +191,7 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(result).to.equal(DROP_RIGHT);
+      expect(result).toBe(DROP_RIGHT);
     });
   });
 
@@ -214,7 +212,7 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(result).to.equal(DROP_LEFT);
+      expect(result).toBe(DROP_LEFT);
     });
 
     it('should return DROP_RIGHT if component HAS children, and clientOffset is NOT near top/bottom sibling boundary', () => {
@@ -233,7 +231,7 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(result).to.equal(DROP_RIGHT);
+      expect(result).toBe(DROP_RIGHT);
     });
 
     it('should return DROP_TOP regardless of component children if clientOffset IS near top sibling boundary', () => {
@@ -266,8 +264,8 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(noChildren).to.equal(DROP_TOP);
-      expect(withChildren).to.equal(DROP_TOP);
+      expect(noChildren).toBe(DROP_TOP);
+      expect(withChildren).toBe(DROP_TOP);
     });
 
     it('should return DROP_BOTTOM regardless of component children if clientOffset IS near bottom sibling boundary', () => {
@@ -300,8 +298,8 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(noChildren).to.equal(DROP_BOTTOM);
-      expect(withChildren).to.equal(DROP_BOTTOM);
+      expect(noChildren).toBe(DROP_BOTTOM);
+      expect(withChildren).toBe(DROP_BOTTOM);
     });
   });
 
@@ -323,7 +321,7 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(result).to.equal(DROP_TOP);
+      expect(result).toBe(DROP_TOP);
     });
 
     it('should return DROP_BOTTOM if component HAS children, and clientOffset is NOT near left/right sibling boundary', () => {
@@ -343,7 +341,7 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(result).to.equal(DROP_BOTTOM);
+      expect(result).toBe(DROP_BOTTOM);
     });
 
     it('should return DROP_LEFT regardless of component children if clientOffset IS near left sibling boundary', () => {
@@ -378,8 +376,8 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(noChildren).to.equal(DROP_LEFT);
-      expect(withChildren).to.equal(DROP_LEFT);
+      expect(noChildren).toBe(DROP_LEFT);
+      expect(withChildren).toBe(DROP_LEFT);
     });
 
     it('should return DROP_RIGHT regardless of component children if clientOffset IS near right sibling boundary', () => {
@@ -414,8 +412,8 @@ describe('getDropPosition', () => {
           },
         }),
       );
-      expect(noChildren).to.equal(DROP_RIGHT);
-      expect(withChildren).to.equal(DROP_RIGHT);
+      expect(noChildren).toBe(DROP_RIGHT);
+      expect(withChildren).toBe(DROP_RIGHT);
     });
   });
 });