Write Unit Test For With NestJS 2023

To write unit tests for a NestJS application, you will need to use a testing framework such as Jest or Mocha. In this example, we will use Jest.

First, you will need to install Jest as a dev dependency in your project:

npm install --save-dev jest

Next, you will need to create a test file for your unit test. Test files should be placed in a __tests__ directory within your project, or you can use the .spec.ts or .test.ts file extension.

Here's an example of a simple unit test for a NestJS service:

import { Test } from '@nestjs/testing';
import { MyService } from './my.service';

describe('MyService', () => {
  let service: MyService;

  beforeEach(async () => {
    const module = await Test.createTestingModule({
      providers: [MyService],
    }).compile();

    service = module.get<MyService>(MyService);
  });

  it('should be defined', () => {
    expect(service).toBeDefined();
  });

  it('should return "Hello, world!"', () => {
    expect(service.sayHello()).toEqual('Hello, world!');
  });
});

In this example, we are using the Test class from @nestjs/testing to create a testing module that includes the MyService provider. We then use the module.get method to retrieve an instance of the service, which we can use to run our tests.

To run your unit tests, you can use the npm test command. This will execute all of the tests in your project and report the results.