mongoose.connect is not a function when running tests

[alsoicode]

I would like to create an e2e test for a module that is reliant on MongooseService.

When I run my test:

// mongoose.service.ts

import { Component, Logger } from '@nestjs/common';
import * as mongoose from 'mongoose';

@Component()
export class MongooseService {
  private readonly logger = new Logger(MongooseService.name);

  private instance: mongoose.Connection;

  constructor() {
    (mongoose as any).Promise = global.Promise;
  }

  get connection() {
    if (this.instance) {
      return this.instance;
    }
    else {
      mongoose.connect(process.env.MONGODB_URI, { useMongoClient: true });
      this.instance = mongoose.connection;

      this.instance.on('error', (e: Error) => {
        this.logger.error('MongoDB conenction error:' + e);
      });

      this.instance.once('open', () => {
        this.logger.log('Successful MongoDB Connection');
      });

      return this.instance;
    }
  }

}


// unsubscribes.module.ts

import { UnsubscribeRequestModel } from './unsubscribes.model';

@Module({
  modules: [
    SharedModule,
  ],
  controllers: [
    UnsubscribesController,
  ],
  components: [
    UnsubscribeRequestModel,
  ],
  exports: [
    UnsubscribeRequestModel,
  ],
})
export class UnsubscribesModule {

  public configure(consumer: MiddlewaresConsumer) {
    consumer
      .apply(PassportMiddleware)
      .forRoutes(UnsubscribesController);
  }

}


// unsubscribes.spec.ts

describe('Controller', () => {
    beforeAll(async () => {
      const unsubscribesModule = await Test.createTestingModule({
        modules: [
          SharedModule,
          UnsubscribesModule,
        ],
      }).compile();

      const app = unsubscribesModule.createNestApplication(server);
      await app.init();
    });

    it('should not throw an exception', async () => {
      expect(true).toBe(true);
    });
  });

I always get "mongoose.connect is not a function". I've tried manually providing the value in the components:

components: [{ provide: MongooseService, useValue: mongoose }],

and

components: [{ provide: 'MongooseService', useFactory: () =>  new MongooseService(), inject: [MongooseService] }],

but am coming up short. Any helpful hints?