How to unit test Controller and mock @InjectModel in the Service constructor

Question

I am getting issues while unit testing my controller and getting an error "Nest can't resolve dependencies of my service".

For maximum coverage I wanted to unit test controller and respective services and would like to mock external dependencies like mongoose connection. For the same I already tried suggestions mentioned in the below link but didn't find any luck with that:

https://github.com/nestjs/nest/issues/194#issuecomment-342219043

Please find my code below:

export const deviceProviders = [
    {
        provide: 'devices',
        useFactory: (connection: Connection) => connection.model('devices', DeviceSchema),
        inject: ['DbConnectionToken'],
    },
];


export class DeviceService extends BaseService {
    constructor(@InjectModel('devices') private readonly _deviceModel: Model<Device>) {
        super();
    }

    async getDevices(group): Promise<any> {
        try {
            return await this._deviceModel.find({ Group: group }).exec();
        } catch (error) {
            return Promise.reject(error);
        }
    }
}


@Controller()
export class DeviceController {
    constructor(private readonly deviceService: DeviceService) {
    }

   @Get(':group')
   async getDevices(@Res() response, @Param('group') group): Promise<any> {
        try {
            const result = await this.deviceService.getDevices(group);
            return response.send(result);
        }
        catch (err) {
            return response.status(422).send(err);
        }
    }
}


@Module({
    imports: [MongooseModule.forFeature([{ name: 'devices', schema: DeviceSchema }])],
    controllers: [DeviceController],
    components: [DeviceService, ...deviceProviders],
})
export class DeviceModule { }

Unit test:

describe('DeviceController', () => {
    let deviceController: DeviceController;
    let deviceService: DeviceService;

    const response = {
        send: (body?: any) => { },
        status: (code: number) => response,
    };

    beforeEach(async () => {
        const module = await Test.createTestingModule({
            controllers: [DeviceController],
            components: [DeviceService, ...deviceProviders],
        }).compile();

        deviceService = module.get<DeviceService>(DeviceService);
        deviceController = module.get<DeviceController>(DeviceController);
    });

    describe('getDevices()', () => {
        it('should return an array of devices', async () => {
            const result = [{
                Group: 'group_abc',
                DeviceId: 'device_abc',
            },
            {
                Group: 'group_xyz',
                DeviceId: 'device_xyz',
            }];
            jest.spyOn(deviceService, 'getDevices').mockImplementation(() => result);

            expect(await deviceController.getDevices(response, null)).toBe(result);
        });
    });
});

When I am running my test case above, I am getting two errors:

Nest can't resolve dependencies of the DeviceService (?). Please make sure that the argument at index [0] is available in the current context.

Cannot spyOn on a primitive value; undefined given

jkchao · Accepted Answer · 2018-10-24T03:00:31.393

Example code:

import { Test } from '@nestjs/testing';

import { getModelToken } from '@nestjs/mongoose';


describe('auth', () => {
  let deviceController: DeviceController;
  let deviceService: DeviceService;

  const mockRepository = {
    find() {
      return {};
    }
  };

  beforeAll(async () => {
    const module = await Test.createTestingModule({
      imports: [DeviceModule]
    })
      .overrideProvider(getModelToken('Auth'))
      .useValue(mockRepository)
      .compile();

    deviceService = module.get<DeviceService>(DeviceService);
  });

  // ...


});

score 4 · Answer 2 · answered Oct 19 '18 at 10:01

4

You are not injecting the correct token here. Instead of a plain string you have to use the function getModelToken.

import { getModelToken } from '@nestjs/mongoose';

// ...

{ provide: getModelToken('devices'), useFactory: myFactory },

answered Oct 19 '18 at 10:01

Kim Kern

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score 0 · Answer 3 · answered Dec 13 '22 at 14:43

Here is the solution provided by this repo. See the mongo-sample. I am testing my API using the @injectModel and another service. Here's the snippet:

import { CategoriesService } from './../categories/categories.service';
import { getModelToken } from '@nestjs/mongoose';
import { Test, TestingModule } from '@nestjs/testing';
import { ProductsService } from './products.service';

describe('ProductsService', () => {
  let service: ProductsService;

  beforeAll(async () => {
    const module: TestingModule = await Test.createTestingModule({
      // getModelToken to mock the MongoDB connection
      providers: [
        ProductsService,
        CategoriesService,
        {
          provide: getModelToken('Product'),
          useValue: {
            find: jest.fn(),
            findOne: jest.fn(),
            findByIdAndUpdate: jest.fn(),
            findByIdAndRemove: jest.fn(),
            save: jest.fn(),
          },
        },
        {
          provide: getModelToken('Category'),
          useValue: {
            find: jest.fn(),
            findOne: jest.fn(),
            findByIdAndUpdate: jest.fn(),
            findByIdAndRemove: jest.fn(),
            save: jest.fn(),
          },
        },
      ],
    }).compile();

    service = module.get<ProductsService>(ProductsService);
  });
  // your test case
});

How to unit test Controller and mock @InjectModel in the Service constructor

3 Answers3

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