TypeScript-Tutorial

TypeScript Tutorial

Installing and configuring jest for TypeScript

• In root folder of the project, install jest:

npm i -D jest

• Installing types for TypeScript jest

npm i -D @types

• Installing ts-test which compiles first and then run the tests

npm i -D ts-jest

• Creating a file jest.config.js in the root of the project and pass this in it:

module.exports = {
   preset: 'ts-jest',
   testEnvironment: 'node',
   };

• In package.json put this:

"scripts": {
    "test": "jest",
    "built": "tsc"
},

• Create a test file named just like the file you want to test.
  • Example: the file we want to test: foo.ts
  • Example: the test file named: foo.test.ts

Testing the files

• To see if the configuration is properly installed, just write a test like this:

  • In foo.ts

  export function boo(a, b) {
    return a + b;
  }
  

  • In foo.test.ts

  import { boo } from './foo';
  
  describe('Testing boo()', () => {
    it('boo(3, 5): return 8', () => {
      expect(boo(3, 5).toBe(8),
    }),
  });
  

• Now run the test

run test