README.md

NestJS Microservices TestBed

Do yo find it hard to implement integration (e2e) tests for your NestJS microservices without having to run the real broker?

This project aims to provide a similar testing experience to testing a NestJS HTTP server without having to spin it up.

The library provides a MicroserviceTestBed class that acts as a "broker" and exposes a custom microservice Transporter which plugs into the NestJS microservice abstraction.

This way, you can "emit" messages to the test bed and your application would handle them as if they were coming from a real broker. This way you can easily test

⚠️ Warning 🏗 Under construction 🚧

This library is still in a very early stage of development and does not yet support all the features of the NestJs microservices abstraction, namely, there is no support for the @Context decorator yet nor for any platform-specific features of other transporters.

Example

// ...other imports
import { TestBedClient } from '@nestjs-microservices-testbed/core';
import waitForExpect from 'wait-for-expect';

class ExclamationInterceptor implements NestInterceptor {
    intercept(context: ExecutionContext, next: CallHandler<any> ): Observable<any> {
        return next.handle()
            .pipe(map((result) => result + '!'));
    }
}

@Controller()
class TestAppConsumer {

    constructor(
        @Inject('TEST_CLIENT')
        private readonly client: ClientProxy,
    ) {}

    @MessagePattern('say-hello')
    @UseInterceptors(ExclamationInterceptor)
    async helloWorld(@Payload() data: string) {
        return `Hello ${data}`;
    }

    returnResponse() {
        return firstValueFrom(this.client.send('handle-response', ''));
    }

    @MessagePattern('handle-response')
    handleResponse() {
        return 'Response!';
    }

    @EventPattern('events')
    handleEvent(@Payload() data: string) {
        this.client.emit('emitted-events', data).subscribe();
    }
}


describe('Microservices Testbed', () => {

    // create instance of the test bed
    const testBed = new MicroservicesTestBed();
    let app: INestMicroservice;

    beforeAll(async () => {
        const module = await Test.createTestingModule({
            imports: [
                ClientsModule.register([{
                    name: 'TEST_SERVICE',
                    // register a custom class to be used as the client
                    customClass: testBed.getClientClass(),
                }]);
            ]
            controllers: [TestAppConsumer],
        })
        app = module.createNestMicroservice<MicroserviceOptions>({
            // retrieve the test bed server instance
            strategy: testBed.getServerInstance(),
        });
        await app.init();
    });

    afterAll(() => app.close());

    it('should handle message pattern', async () => {
        // send a message using the test bed
        const result = await testBed.handleMessage({
            pattern: 'hello-world',
            data: 'World',
        });
        // observe that your application handled the message
        // and the interceptor was triggered
        expect(result).toBe('Hello World!');
    });

    it('should handle client response', async () => {
        // invoke a method that sends a message using the client
        const result = await app.get(TestAppConsumer).returnResponse();
        // observe that a response was received through the client
        expect(result).toBe('Response!');
    });

    it('should handle event pattern', async () => {
        // emit an event using the test bed
        testBed.handleEvent({
            pattern: 'events',
            data: 'event-payload',
        });
        await waitForExpect(() => {
            // verify that your application handled the event
            // by checking that it emitted another event
            expect(
                testBed.getLastMessageForPattern('emitted-events').data
            ).toEqual(['event-payload']);
        });
    });
});