Integrate Jest to Angular App

1. Create your angular app
2. Install jest
   npm install jest jest-preset-angular @types/jest
3. In your project root, create a setup-jest.ts file with the following contents:
   import 'jest-preset-angular/setup-jest';
4. Create the jest.config.js file in your project root directory with the following contents:

   module.exports = {
     preset: 'jest-preset-angular',
     setupFilesAfterEnv: ['<rootDir>/setup-jest.ts'],
     globalSetup: 'jest-preset-angular/global-setup',
   };

5. Adjust your tsconfig.spec.json in your project root

   {
      "extends": "./tsconfig.json",  
      "compilerOptions": {  
         "outDir": "./out-tsc/spec",  
         "module": "CommonJs",  
         "types": ["jest"]  
      },  
      "include": ["src/**/*.spec.ts", "src/**/*.d.ts"]  
    };

6. update package.json file in your project root as below.

   "test": "jest --verbose",
   "test:watch": "jest --watch"

7. Open your terminal and run npm run test, enjoy!
8. If you want to remove karma and Jasmine and switch to Jest completely, run the following command.

   npm uninstall karma karma-chrome-launcher karma-coverage-istanbul-reporter karma-jasmine karma-jasmine-html-reporter jasmine-core jasmine-spec-reporter

references:

xfive.co/blog/testing-angular-faster-jest/