Nestjs tests pass in local environment but fail on a GitLab pipeline

The behavior is as the title describes it. I've tried a number of things but can't figure out why this is happening.

This error was fixed by adding a Jest timeout:

  ● AppController › /ping › Return "Pong!"
    thrown: "Exceeded timeout of 15000 ms for a hook.
    Use jest.setTimeout(newTimeout) to increase the timeout value, if this is a long-running test."
      19 |   let nestApp: INestApplication;
      20 |
    > 21 |   beforeAll(async () => {
         |   ^
      22 |     app = await Test.createTestingModule({
      23 |       controllers: [AppController],
      24 |       providers: [
      at src/app/app.controller.spec.ts:21:3
      at Object.<anonymous> (src/app/app.controller.spec.ts:15:1)

Then I get this error:

  ● AppController › / › Return "Pong!"
    Instance Exited before being ready and without throwing an error!
      at MongoInstance.<anonymous> (../../node_modules/mongodb-memory-server-core/src/util/MongoInstance.ts:338:13)
      at MongoInstance.closeHandler (../../node_modules/mongodb-memory-server-core/src/util/MongoInstance.ts:513:10)

The problematic tests (just showing one of them for brevity's sake) are:

describe('AppController', () => {
  let app: TestingModule;
  let nestApp: INestApplication;

  beforeAll(async () => {
    app = await Test.createTestingModule({
      controllers: [AppController],
      providers: [
        AppService,
        { provide: APP_PIPE, useValue: new ValidationPipe() },
      ],
      imports: [
        HttpModule,
        AuthzModule,
        BullzModule,
        AgendazModule,
        MongosezModule,
        TestDatabaseModule,
      ],
    }).compile();
    nestApp = app.createNestApplication();
    await nestApp.init();
    return;
  });

  describe('/ping', () => {
    test('Return "Pong!"', async () => {
      const appServiceSpy = jest.spyOn(AppService.prototype, 'ping');
      appServiceSpy.mockReturnValue({ message: 'Pong!' });
      const response = await supertest(nestApp.getHttpServer()).get('/ping');
      expect(response.body).toStrictEqual({
        message: 'Pong!',
      });

      return;
    });

    return;
  });

return;
});

The problems started to happening when I added Mongoose to the application. The TestDatabaseModule simply connects to an in memory database for testing (this package).

MongoosezModule:

@Module({
  imports: [
    NestMongooseModule.forFeature([
      { name: NewsCache.name, schema: NewsCacheSchema },
    ]),
  ],
  providers: [NewsCacheService],
  exports: [NewsCacheService],
})
export class MongoosezModule {}

TestDatabaseModule:

@Module({
  imports: [
    NestMongooseModule.forRootAsync({
      useFactory: async () => {
        const mongod = await MongoMemoryServer.create();
        const uri = mongod.getUri();
        return {
          uri: uri,
        };
      },
    }),
  ],
})
export class TestDatabaseModule {}

Some tests pass just fine, for example:

describe('AppService', () => {
  let service: AppService;
  let http: HttpService;

  beforeAll(async () => {
    const app = await Test.createTestingModule({
      providers: [
        AppService,
        NewsCacheService,
        {
          provide: getModelToken(NewsCache.name),
          useValue: newsCacheModelMock,
        },
      ],
      imports: [HttpModule],
    }).compile();
    service = app.get<AppService>(AppService);
    http = app.get<HttpService>(HttpService);
    return;
  });

  describe('When getNews is called..', () => {
    test('A GET query is made to a generated URL.', () => {
      const expected =
        `${environment.newsApiUrl}/everything` +
        `?apiKey=${environment.newsApiKey}` +
        `&q=test0 AND test1` +
        `&sortBy=popularity` +
        `&to=${service.getTodaysDate()}` +
        `&language=en` +
        `&pageSize=10` +
        `&page=3`;
      const httpSpy = jest.spyOn(http, 'get');
      service.getNews('test0,test1', 3);
      expect(httpSpy).toHaveBeenCalledWith(expected);
      return;
    });  

  return;
});

The tests are run with nx test $APP --code-coverage --coverageReporters="text" --detectOpenHandles --verbose.

I've tried using three different Node.js images for the pipeline:

• node:14.18.2
• node:16.11.1
• node:16.11.1-slim