Angular unit-test using Jest and Angular-Testing-Library

Install Angular

npm i -g @angular/cli
ng new angular-test-app
cd angular-test-app
ng serve --open

Install Angular-Testing-Library

npm i --save-dev @testing-library/angular @testing-library/jest-dom

Install Jest and Setting up Jest

// Install the needed dependencies
npm i jest @types/jest jest-preset-angular --save-dev

// or
yarn add jest jest-preset-angular @types/jest --dev

Uninstall Karma

npm uninstall karma karma-chrome-launcher karma-coverage-istanbul-reporter karma-jasmine karma-jasmine-html-reporter @types/jasmine @types/jasminewd2 jasmine-core jasmine-spec-reporter

// or
yarn remove karma karma-chrome-launcher karma-coverage-istanbul-reporter karma-jasmine karma-jasmine-html-reporter

Remove karma configuraion file

rm karma.conf.js

Remove test from angular.json

Remove the test section from angular.json, this section looks like the following:

// angular.json
"test": {
       "builder": "@angular-devkit/build-angular:karma",
       "options": {
         "main": "src/test.ts",
         "polyfills": "src/polyfills.ts",
         "tsConfig": "tsconfig.spec.json",
         "karmaConfig": "karma.conf.js",
         "assets": [
           "src/favicon.ico",
           "src/assets"
         ],
         "styles": [
           "src/styles.scss"
         ],
         "scripts": []
       }
     },
// REMOVE ALL "test" section

Remove files: karma.conf.js and src/test.ts

Create file: setupJest.ts

and Add to this file should have the following:

// setupJest.ts
import 'jest-preset-angular';
import 'jest-preset-angular/setup-jest';

Modify file: tsconfig.spec.json

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "outDir": "./out-tsc/spec",
    "types": [
      "jest",
      "node",
      "@testing-library/jest-dom"
    ],
    "esModuleInterop": true,
    "emitDecoratorMetadata": true
  },
  "files": [
    "src/polyfills.ts"
  ],
  "include": [
    "src/**/*.spec.ts",
    "src/**/*.d.ts"
  ]
}

Modify file: package.json

 "scripts": {
   "test": "jest",
   "test:coverage": "jest --coverage"
 }


## Add to `package.json`

> Add Jest configuration to the end of this file

```js
"jest": {
    "preset": "jest-preset-angular",
    "setupFilesAfterEnv": [
      "<rootDir>/setupJest.ts"
    ],
    "testPathIgnorePatterns": [
      "<rootDir>/node_modules/",
      "<rootDir>/dist/"
    ],
    "globals": {
      "ts-jest": {
        "tsconfig": "<rootDir>/tsconfig.spec.json",
        "stringifyContentPathRegex": "\\.html$"
      }
    }
}

Add to: tsconfig.json

"compilerOptions": {
  "allowSyntheticDefaultImports": true,
}

Setup Angular-testing-library

// tsconfig.spec.json
// add "@testing-library/jest-dom"
"types": [
  "node",
  "jest",
  "@testing-library/jest-dom"
],

Test Jest

run the test for: src/app/app.component.spec.ts

// run ones
yarn test

// or
npx jest

// watch for changes
yarn test --watch

// watch only one
yarn test async.component.spec.ts --watch

Coverage

The coverage as built-in functionality is generated in: ./coverage directory

Demo

Extra note:

The .compileComponents() object is called to compile your component's resources like the template, styles, etc. You might not necessarily need to compile your component if you are using Webpack.

beforeEach(async(() => {
   TestBed.configureTestingModule({
      declarations: [
         AppComponent
      ],
   }).compileComponents(); <-- Don't need it when using WebPack
}));

---

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