How to do unit testing to @Inject with ClientKafka in NestJS

Question

I need to do some unit test to a kafka implementation in my project with NestJS but I don't know how to do it.

I have a Service thats inject a Client Kafka

export class Service {
  private static readonly logger = new Logger(ProducerService.name);

  constructor(
    @Inject('kafka-registrar') private client: ClientKafka,
    private someOtherService: SomeOtherService,
  ) {}

Module

@Module({
  imports: [
    ClientsModule.register([
      {
        name: 'kafka-registrar',
        transport: Transport.KAFKA,
        options: {
          client: {
            clientId: 'hero',
            brokers: ['localhost:9092'],
          },
          consumer: {
            groupId: '1',
          },
        },
      },
    ]),
    SomeOtherService,
  ],
  providers: [Service],
})
export class Module {}

Unit test

describe('Test Controller', () => {
  let clientKafka: ClientKafka;
  let someOtherService: SomeOtherService;
  let producerService: ProducerService;

  beforeEach(async () => {
    const moduleRef = await Test.createTestingModule({
      providers: [
        ProducerService,
        {
          provide: SchemaRegistryService,
          useValue: {
            encodeWithId: jest.fn(),
          },
        },
        {
          provide: ClientKafka,
          useValue: {
            emit: jest.fn(),
          },
        },
      ],
    }).compile()

    clientKafka = moduleRef.get(ClientKafka);
    schemaRegistryService = moduleRef.get(SchemaRegistryService);
    producerService = moduleRef.get(ProducerService);
  });

The project give me this error:

Error: Nest can't resolve dependencies of the ProducerService (?, SchemaRegistryService). Please make sure that the argument kafka-registrar at index [0] is available in the RootTestModule context.

Potential solutions:
- If kafka-registrar is a provider, is it part of the current RootTestModule?
- If kafka-registrar is exported from a separate @Module, is that module imported within RootTestModule?
  @Module({
    imports: [ /* the Module containing kafka-registrar */ ]
  })

I don't know how to resolve this in NestJS. For example in Java,I belive that this can be with @Mock ClientKafka clientKafka bit I dont have any other experience with NestJS... Please helpme! :)

score 3 · Answer 1 · answered Apr 08 '22 at 08:30

In your test file, you can change provide: ClientKafka to this provide: 'kafka-registrar'.

const moduleRef = await Test.createTestingModule({
  providers: [
    ProducerService,
    {
      provide: SchemaRegistryService,
      useValue: {
        encodeWithId: jest.fn(),
      },
    },
    {
      provide: 'kafka-registrar',
      useValue: {
        emit: jest.fn(),
      },
    },
  ],
}).compile()

How to do unit testing to @Inject with ClientKafka in NestJS

1 Answers1