Test NestJS Service against Actual Database

Question

I would like to be able to test my Nest service against an actual database. I understand that most unit tests should use a mock object, but it also, at times, makes sense to test against the database itself.

I have searched through SO and the GH issues for Nest, and am starting to reach the transitive closure of all answers. :-)

I am trying to work from https://github.com/nestjs/nest/issues/363#issuecomment-360105413. Following is my Unit test, which uses a custom provider to pass the repository to my service class.

describe("DepartmentService", () => {
  const token = getRepositoryToken(Department);
  let service: DepartmentService;
  let repo: Repository<Department>;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [
        DepartmentService,
        {
          provide: token,
          useClass: Repository
        }
      ]
    }).compile();

    service = module.get<DepartmentService>(DepartmentService);
    repo = module.get(token);
  });

Everything compiles properly, TypeScript seems happy. However, when I try to execute create or save on my Repository instance, the underlying Repository appears to be undefined. Here's the stack backtrace:

TypeError: Cannot read property 'create' of undefined

  at Repository.Object.<anonymous>.Repository.create (repository/Repository.ts:99:29)
  at DepartmentService.<anonymous> (relational/department/department.service.ts:46:53)
  at relational/department/department.service.ts:19:71
  at Object.<anonymous>.__awaiter (relational/department/department.service.ts:15:12)
  at DepartmentService.addDepartment (relational/department/department.service.ts:56:16)
  at Object.<anonymous> (relational/department/test/department.service.spec.ts:46:35)
  at relational/department/test/department.service.spec.ts:7:71

It appears that the EntityManager instance with the TypeORM Repository class is not being initialized; it is the undefined reference that this backtrace is complaining about.

How do I get the Repository and EntityManager to initialize properly?

thanks, tom.

Answer 1

To initialize typeorm properly, you should just be able to import the TypeOrmModule in your test:

Test.createTestingModule({
  imports: [
   TypeOrmModule.forRoot({
        type: 'mysql',
        // ...
   }),
   TypeOrmModule.forFeature([Department])
  ]

Answer 2

I prefer not using @nestjs/testing for the sake of simplicity.

First of all, create a reusable helper:

/* src/utils/testing-helpers/createMemDB.js */
import { createConnection, EntitySchema } from 'typeorm'
type Entity = Function | string | EntitySchema<any>

export async function createMemDB(entities: Entity[]) {
  return createConnection({
    // name, // let TypeORM manage the connections
    type: 'sqlite',
    database: ':memory:',
    entities,
    dropSchema: true,
    synchronize: true,
    logging: false
  })
}

Then, write test:

/* src/user/user.service.spec.ts */
import { Connection, Repository } from 'typeorm'
import { createMemDB } from '../utils/testing-helpers/createMemDB'
import UserService from './user.service'
import User from './user.entity'

describe('User Service', () => {
  let db: Connection
  let userService: UserService
  let userRepository: Repository<User>

  beforeAll(async () => {
    db = await createMemDB([User])
    userRepository = await db.getRepository(User)
    userService = new UserService(userRepository) // <--- manually inject
  })
  afterAll(() => db.close())

  it('should create a new user', async () => {
    const username = 'HelloWorld'
    const password = 'password'

    const newUser = await userService.createUser({ username, password })
    expect(newUser.id).toBeDefined()

    const newUserInDB = await userRepository.findOne(newUser.id)
    expect(newUserInDB.username).toBe(username)
  })
})

Refer to https://github.com/typeorm/typeorm/issues/1267#issuecomment-483775861

Answer 3

Here's an update to the test that employs Kim Kern's suggestion.

describe("DepartmentService", () => {
  let service: DepartmentService;
  let repo: Repository<Department>;
  let module: TestingModule;

  beforeAll(async () => {
    module = await Test.createTestingModule({
      imports: [
        TypeOrmModule.forRoot(),
        TypeOrmModule.forFeature([Department])
      ],
      providers: [DepartmentService]
    }).compile();

    service = module.get<DepartmentService>(DepartmentService);
    repo = module.get<Repository<Department>>(getRepositoryToken(Department));
  });

  afterAll(async () => {
    module.close();
  });

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

  // ...
}