refactor(tests): fix memory leak, intermittent failures

.eslintrc

@@ -73,7 +73,10 @@
     // https://nolanlawson.com/2018/03/20/smaller-lodash-bundles-with-webpack-and-babel/
     "lodash/chaining": [2, "never"],
     "lodash/import-scope": [2, "method"],
-    "react/destructuring-assignment": [2, "always", { "ignoreClassFields": true }]
+    "react/destructuring-assignment": [2, "always", { "ignoreClassFields": true }],
+    "jest/expect-expect": "error",
+    "jest/prefer-hooks-on-top": "error"
+    // "jest/consistent-test-it": ["error", { "fn": "test", "withinDescribe": "it" }]
   },
   // Testcases have less eslint rules applied to them
   "overrides": [

.travis.yml

@@ -23,7 +23,7 @@ install:
 
 script:
   - yarn lint
-  - travis_wait yarn test --runInBand --ci  --coverage && cat ./coverage/lcov.info | yarn run coveralls && rm -rf ./coverage # report coveralls status
+  - travis_wait yarn test --maxWorkers=2 --ci --logHeapUsage --coverage && cat ./coverage/lcov.info | yarn run coveralls && rm -rf ./coverage # report coveralls status
 
 after_success:
   - yarn publish-npm

.vscode/launch.json

@@ -6,12 +6,14 @@
   "configurations": [
     {
       "type": "node",
+      "runtimeVersion": "10.15.3",
       "request": "launch",
       "name": "Launch Program",
       "program": "${workspaceFolder}/lib/index.js"
     },
     {
       "type": "node",
+      "runtimeVersion": "10.15.3",
       "request": "launch",
       "name": "Jest All",
       "program": "${workspaceFolder}/node_modules/.bin/jest",
@@ -26,6 +28,7 @@
     },
     {
       "type": "node",
+      "runtimeVersion": "10.15.3",
       "request": "launch",
       "name": "Jest Current File",
       "program": "${workspaceFolder}/node_modules/.bin/jest",

config/jest/cssTransform.js

@@ -1,7 +1,7 @@
 'use strict';
 
 // This is a custom Jest transformer turning style imports into empty objects.
-// http://facebook.github.io/jest/docs/tutorial-webpack.html
+// https://jestjs.io/docs/en/webpack
 module.exports = {
   process() {
     return 'module.exports = {};';

config/jest/fileTransform.js

@@ -3,7 +3,7 @@
 const path = require('path');
 
 // This is a custom Jest transformer turning file imports into filenames.
-// http://facebook.github.io/jest/docs/tutorial-webpack.html
+// https://jestjs.io/docs/en/webpack
 module.exports = {
   process(src, filename) {
     return `module.exports = ${JSON.stringify(path.basename(filename))};`;

config/jest/setupTest.js

@@ -1 +1,7 @@
 import 'jest-styled-components';
+
+beforeEach(() => {
+  // Every test we write should have at least one assertion. If this fails, we need to look at the invoking test to ensure there's not a promise being swallowed or something.
+  // Review this for more context: https://github.com/IBM/carbon-addons-iot-react/issues/1143#issuecomment-623577505
+  expect.hasAssertions();
+});

jest.config.js

@@ -86,6 +86,7 @@ module.exports = {
     __DEV__: false,
   },
   setupFiles: ['<rootDir>/config/jest/setup.js'],
+  testEnvironment: 'jest-environment-jsdom-sixteen',
   setupFilesAfterEnv: ['<rootDir>/config/jest/setupTest.js'],
   testMatch: [
     '<rootDir>/**/__tests__/**/*.js?(x)',

package.json

@@ -150,13 +150,12 @@
     "@storybook/addon-storyshots": "^5.3.17",
     "@storybook/addons": "^5.3.17",
     "@storybook/react": "^5.3.17",
-    "@testing-library/dom": "^6.10.1",
-    "@testing-library/jest-dom": "^5.0.2",
-    "@testing-library/react": "^9.3.2",
+    "@testing-library/dom": "^7.2.2",
+    "@testing-library/jest-dom": "^5.5.0",
+    "@testing-library/react": "^10.0.3",
     "autoprefixer": "^9.4.4",
     "babel-core": "^7.0.0-bridge.0",
     "babel-eslint": "^10.1.0",
-    "babel-jest": "^25.3.0",
     "babel-loader": "^8.1.0",
     "babel-plugin-dev-expression": "^0.2.2",
     "babel-plugin-lodash": "^3.3.4",
@@ -178,7 +177,7 @@
     "eslint-config-prettier": "^4.1.0",
     "eslint-plugin-babel": "^5.3.0",
     "eslint-plugin-import": "^2.14.0",
-    "eslint-plugin-jest": "^22.1.2",
+    "eslint-plugin-jest": "^23.8.2",
     "eslint-plugin-jsx-a11y": "^6.1.2",
     "eslint-plugin-lodash": "^5.1.0",
     "eslint-plugin-prettier": "^3.0.1",
@@ -189,9 +188,9 @@
     "file-loader": "^4.0.0",
     "full-icu": "^1.3.1",
     "husky": "^1.3.1",
-    "jest": "^24.9.0",
+    "jest": "^25.5.1",
+    "jest-environment-jsdom-sixteen": "^1.0.3",
     "jest-styled-components": "^6.3.1",
-    "jsdom": "^15.2.1",
     "lint-staged": "^8.1.0",
     "moment-timezone": "^0.5.26",
     "node-sass": "^4.12.0",
@@ -225,6 +224,8 @@
     "stylelint": "^10.1.0",
     "stylelint-config-recommended-scss": "^3.3.0",
     "stylelint-scss": "^3.10.0",
+    "weak": "^1.0.1",
+    "weak-napi": "^2.0.1",
     "webpack": "^4.28.4",
     "whatwg-fetch": "^3.0.0"
   },

src/components/Breadcrumb/Breadcrumb.test.jsx

@@ -8,9 +8,6 @@ const commonProps = {
   onClick: () => console.log('clicked'),
 };
 
-const originalOffsetHeight = Object.getOwnPropertyDescriptor(HTMLElement.prototype, 'clientWidth');
-const originalOffsetWidth = Object.getOwnPropertyDescriptor(HTMLElement.prototype, 'scrollWidth');
-
 describe('Breadcrumb', () => {
   test('overflows when container is smaller than breadcrumbs', () => {
     const { container } = render(
@@ -39,8 +36,8 @@ describe('Breadcrumb with overflow', () => {
   });
 
   afterAll(() => {
-    Object.defineProperty(HTMLElement.prototype, 'clientWidth', originalOffsetHeight);
-    Object.defineProperty(HTMLElement.prototype, 'scrollWidth', originalOffsetWidth);
+    delete HTMLElement.prototype.clientWidth;
+    delete HTMLElement.prototype.scrollWidth;
   });
 
   test('overflows when container is smaller than breadcrumbs', () => {
@@ -55,15 +52,26 @@ describe('Breadcrumb with overflow', () => {
   });
 
   describe('has dev console warning(s)', () => {
-    const originalConsole = console.error;
     const originalDev = window.__DEV__;
     const originalResizeObserver = window.ResizeObserver;
 
-    // Applies only to tests in this describe block
+    beforeAll(() => {
+      jest.spyOn(console, 'error').mockImplementation(() => {});
+    });
+
     beforeEach(() => {
       window.__DEV__ = true;
       window.ResizeObserver = undefined;
-      console.error = jest.fn();
+    });
+
+    afterEach(() => {
+      console.error.mockClear();
+      window.__DEV__ = originalDev;
+      window.ResizeObserver = originalResizeObserver;
+    });
+
+    afterAll(() => {
+      console.error.mockRestore();
     });
 
     test('when ResizeObserver is not supported in the current environment', () => {
@@ -76,12 +84,5 @@ describe('Breadcrumb with overflow', () => {
       );
       expect(console.error).toHaveBeenCalledTimes(1);
     });
-
-    afterEach(() => {
-      // restore to original values
-      window.__DEV__ = originalDev;
-      window.ResizeObserver = originalResizeObserver;
-      console.error = originalConsole;
-    });
   });
 });

src/components/Card/Card.test.jsx

@@ -1,13 +1,14 @@
 import { mount } from 'enzyme';
 import React from 'react';
-/* eslint-disable*/
 import { Tooltip } from 'carbon-components-react';
-import { render, fireEvent, waitForElement } from '@testing-library/react';
+import { render, fireEvent, waitFor } from '@testing-library/react';
 import { Popup20 } from '@carbon/icons-react';
+
 import { CARD_SIZES, CARD_TITLE_HEIGHT, CARD_ACTIONS } from '../../constants/LayoutConstants';
+import { settings } from '../../constants/Settings';
+
 import CardRangePicker from './CardRangePicker';
 import Card from './Card';
-import { settings } from '../../constants/Settings';
 
 const { iotPrefix } = settings;
 
@@ -19,17 +20,21 @@ const cardProps = {
 };
 
 describe('Card testcases', () => {
-  test('small', () => {
+  it('small', () => {
     const wrapper = mount(<Card {...cardProps} size={CARD_SIZES.SMALL} />);
 
     // small should have full header
     expect(wrapper.find(`.${iotPrefix}--card--header`)).toHaveLength(1);
   });
 
-  test('child size prop', () => {
+  it('child size prop', () => {
     const childRenderInTitleCard = jest.fn();
 
-    mount(<Card title="My Title" size={CARD_SIZES.MEDIUM} children={childRenderInTitleCard} />);
+    mount(
+      <Card title="My Title" size={CARD_SIZES.MEDIUM}>
+        {childRenderInTitleCard}
+      </Card>
+    );
     expect(childRenderInTitleCard).toHaveBeenCalledWith(
       {
         width: 0,
@@ -41,7 +46,7 @@ describe('Card testcases', () => {
 
     const childRenderInNoTitleCard = jest.fn();
 
-    mount(<Card size={CARD_SIZES.MEDIUM} children={childRenderInNoTitleCard} />);
+    mount(<Card size={CARD_SIZES.MEDIUM}>{childRenderInNoTitleCard}</Card>);
     expect(childRenderInNoTitleCard).toHaveBeenCalledWith(
       {
         width: 0,
@@ -52,7 +57,7 @@ describe('Card testcases', () => {
     );
   });
 
-  test('render icons', () => {
+  it('render icons', () => {
     let wrapper = mount(
       <Card {...cardProps} size={CARD_SIZES.SMALL} availableActions={{ range: true }} />
     );
@@ -78,7 +83,7 @@ describe('Card testcases', () => {
     expect(wrapper.find(CardRangePicker)).toHaveLength(0);
   });
 
-  test('additional prop based elements', () => {
+  it('additional prop based elements', () => {
     let wrapper = mount(<Card {...cardProps} size={CARD_SIZES.LARGE} tooltip={tooltipElement} />);
     // tooltip prop will render a tooltip in the header
     expect(wrapper.find(`.${iotPrefix}--card--header`).find(Tooltip)).toHaveLength(1);
@@ -90,16 +95,16 @@ describe('Card testcases', () => {
     );
     expect(wrapper.find(`.${iotPrefix}--card--skeleton-wrapper`)).toHaveLength(1);
   });
-  test('isExpanded', () => {
-    let wrapper = mount(
+  it('isExpanded', () => {
+    const wrapper = mount(
       <Card {...cardProps} isExpanded size={CARD_SIZES.LARGE} tooltip={tooltipElement} />
     );
-    //isExpanded renders the modal wrapper around it
+    // isExpanded renders the modal wrapper around it
     expect(wrapper.find('.bx--modal')).toHaveLength(1);
   });
-  test('card actions', () => {
+  it('card actions', () => {
     const mockOnCardAction = jest.fn();
-    let wrapper = mount(
+    const wrapper = mount(
       <Card
         {...cardProps}
         isExpanded
@@ -116,7 +121,7 @@ describe('Card testcases', () => {
     expect(mockOnCardAction).toHaveBeenCalledWith(cardProps.id, CARD_ACTIONS.CLOSE_EXPANDED_CARD);
 
     mockOnCardAction.mockClear();
-    let wrapper2 = mount(
+    const wrapper2 = mount(
       <Card
         {...cardProps}
         size={CARD_SIZES.LARGE}
@@ -131,9 +136,9 @@ describe('Card testcases', () => {
       .props.onClick();
     expect(mockOnCardAction).toHaveBeenCalledWith(cardProps.id, CARD_ACTIONS.OPEN_EXPANDED_CARD);
   });
-  test('card editable actions', async done => {
+  it('card editable actions', async () => {
     const mockOnCardAction = jest.fn();
-    const { getByRole, getByTitle, getByText } = render(
+    const { getByTitle, getByText } = render(
       <Card
         {...cardProps}
         isEditable
@@ -145,25 +150,24 @@ describe('Card testcases', () => {
     );
     fireEvent.click(getByTitle('Open and close list of options'));
     // Click on the first overflow menu item
-    const firstMenuItem = await waitForElement(() => getByText('Edit card'));
+    const firstMenuItem = await waitFor(() => getByText('Edit card'));
     fireEvent.click(firstMenuItem);
     expect(mockOnCardAction).toHaveBeenCalledWith(cardProps.id, CARD_ACTIONS.EDIT_CARD);
     mockOnCardAction.mockClear();
     // Reopen menu
     fireEvent.click(getByTitle('Open and close list of options'));
-    const secondElement = await waitForElement(() => getByText('Clone card'));
+    const secondElement = await waitFor(() => getByText('Clone card'));
     fireEvent.click(secondElement);
     expect(mockOnCardAction).toHaveBeenCalledWith(cardProps.id, CARD_ACTIONS.CLONE_CARD);
 
     // Reopen menu
     fireEvent.click(getByTitle('Open and close list of options'));
     mockOnCardAction.mockClear();
-    const thirdElement = await waitForElement(() => getByText('Delete card'));
+    const thirdElement = await waitFor(() => getByText('Delete card'));
     fireEvent.click(thirdElement);
     expect(mockOnCardAction).toHaveBeenCalledWith(cardProps.id, CARD_ACTIONS.DELETE_CARD);
-    done();
   });
-  test('card toolbar renders in header only when there are actions', () => {
+  it('card toolbar renders in header only when there are actions', () => {
     const wrapperWithActions = mount(
       <Card {...cardProps} isExpanded size={CARD_SIZES.SMALL} availableActions={{ expand: true }} />
     );