Unit Test

install

npm i --save-dev @nestjs/testing

Testing utilities

import { Test } from "@nestjs/testing";
import { CatsController } from "./cats.controller";
import { CatsService } from "./cats.service";

describe("CatsController", () => {
  let catsController: CatsController;
  let catsService: CatsService;

  beforeEach(async () => {
    const moduleRef = await Test.createTestingModule({
      controllers: [CatsController],
      providers: [CatsService],
    }).compile();

    catsService = moduleRef.get<CatsService>(CatsService);
    catsController = moduleRef.get<CatsController>(CatsController);
  });

  describe("findAll", () => {
    it("should return an array of cats", async () => {
      const result = ["test"];
      jest.spyOn(catsService, "findAll").mockImplementation(() => result);

      expect(await catsController.findAll()).toBe(result);
    });
  });
});

scope가 transient 또는 request 일떄

const moduleRef = await Test.createTestingModule({
  controllers: [CatsController],
  providers: [CatsService],
}).compile();

catsService = await moduleRef.resolve(CatsService);

Auto mocking

npm install --save-dev jest-mock

import { ModuleMocker, MockFunctionMetadata } from "jest-mock";

const moduleMocker = new ModuleMocker(global);

describe("CatsController", () => {
  let controller: CatsController;

  beforeEach(async () => {
    const moduleRef = await Test.createTestingModule({
      controllers: [CatsController],
    })
      .useMocker((token) => {
        const results = ["test1", "test2"];
        if (token === CatsService) {
          return { findAll: jest.fn().mockResolvedValue(results) };
        }
        if (typeof token === "function") {
          const mockMetadata = moduleMocker.getMetadata(
            token
          ) as MockFunctionMetadata<any, any>;
          const Mock = moduleMocker.generateFromMetadata(mockMetadata);
          return new Mock();
        }
      })
      .compile();

    controller = moduleRef.get(CatsController);
  });
});

Overriding globally registered enhancers

providers: [
  {
    provide: APP_GUARD,
    useExisting: JwtAuthGuard,
    // ^^^^^^^^ notice the use of 'useExisting' instead of 'useClass'
  },
  JwtAuthGuard,
],

// spec.ts
const moduleRef = await Test.createTestingModule({
  imports: [AppModule],
})
  .overrideProvider(JwtAuthGuard)
  .useClass(MockAuthGuard)
  .compile();

requset scoped instance

const contextId = ContextIdFactory.create();
jest
  .spyOn(ContextIdFactory, "getByRequest")
  .mockImplementation(() => contextId);

catsService = await moduleRef.resolve(CatsService, contextId);