Test NestJS Service against Actual Database

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.

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])
  ]