600. Testing with Jest

• Testing | NestJS - A progressive Node.js framework
• In nest, you can use any testing framework that you like, as Nest doesn't force any specific tooling.

Unit Testing with Jest

Installation

npm i --save-dev @nestjs/testing

Run Test Commands

npm run test   # for unit tests
npm run test:cov  # for test coverage
npm run test:e2e  # for e2e tests

npm run test:watch -- coffees.service # run specific sile in watch mode

• test files end with [name].spec.ts
  • coffee.controller.spec.ts
  • coffee.service.spec.ts
• write tests as self-explanatory code, check the following example
  • Testing | NestJS - A progressive Node.js framework

describe('findOne', () => {
	describe('when user exists', () => {
	  it('should return user', () => {
		expect(appController.findOne(1)).toEqual({
		  id: 1,
		  name: 'user1',
		});
	  });
	});
	
	describe('when user does not exist', () => {
	  it('should return null', () => {
		expect(appController.findOne(2)).toBeNull();
	  });
	})
})

• close app after running e2e tests
  • nest will give you warning about Jest did not exit one second after the test run has completed
  • to fix this
    • add an afterAll jest method to close the app
    • change beforeEach to beforeAll, we don't want to recreate the whole app in e2e tests for each test

beforeAll(async () => {
	await app.init();
})
 
//tests...

afterAll(async () => {
    await app.close();
})

• npm has a pre-built in option, to make commands run before and after a certain command is executed
  • for example: we can create a test db before running a test and remote the test db after running the test, just using npm
  • to do this, add pre[npmcommand], or/and post[npmcommand]

"pretest:e2e": "docker compose up -d test-db",
"test:e2e": "jest ...",
"posttest:e2e": "docker compose stop test-dp && docker compose rm -f test-db"

HTTP Testing with Supertest

• Testing | NestJS - A progressive Node.js framework
• Keep your e2e test files inside the test directory. The testing files should have a .e2e-spec suffix.
  • coffee.service.e2e-spec.ts

  it(`/GET cats`, () => {
    return request(app.getHttpServer())
      .get('/cats')
      .expect(200)
      .expect({
        data: catsService.findAll(),
      });
  });