CODEWITHSUNDEEP
nestjs
Eric
Eric

Reputation: 1499

How to test a module in NestJs

I'm adding tests on a project and improving coverage. I would like to know how can I test a module definition (mymodule.module.ts file) in NestJs. In particular, I'm testing a main module that imports other modules, one of them inits a db connection, this means that I need to mock the service on the other module, to avoid a real db connection. At this moment I have something like this:

beforeEach(async () => {
    const instance: express.Application = express();

    module = await NestFactory.create(MyModule, instance);
});
describe('module bootstrap', () => {
    it('should initialize entities successfully', async () => {
        controller = module.get(MyController);
        ...

        expect(controller instanceof MyController).toBeTruthy();
    });
});

This works, but I'm sure this can get improvements :)

The ideal thing would be something like overrideComponent method provided by Test.createTestingModule.

P.S: I'm using 4.5.2 version

Upvotes: 8

Views: 23169

Answers (3)

lauthieb
lauthieb

Reputation: 53

You can now test your module (at least for code coverage) by building it that way:

describe('MyController', () => {
    let myController: MyController;

    beforeEach(async () => {
        const module = await Test.createTestingModule({
           imports: [MyModule],
        }).compile();

        myController = module.get<MyController>(MyController);
    });

    it('should the correct value', () => {
        expect(myController.<...>).toEqual(<...>);
    });
});

Upvotes: 5

Shinigami
Shinigami

Reputation: 685

Improved my tests based on @laurent-thiebault answer:

import { Test } from '@nestjs/testing';
import { ThingsModule } from './things.module';
import { ThingsResolver } from './things.resolver';
import { ThingsService } from './things.service';

describe('ThingsModule', () => {
  it('should compile the module', async () => {
    const module = await Test.createTestingModule({
      imports: [ThingsModule],
    }).compile();

    expect(module).toBeDefined();
    expect(module.get(ThingsResolver)).toBeInstanceOf(ThingsResolver);
    expect(module.get(ThingsService)).toBeInstanceOf(ThingsService);
  });
});

Upvotes: 11

Shady Khalifa
Shady Khalifa

Reputation: 187

We usually didn't test .module.ts files directly.

we do this in e2e testing.

but I wonder why one should test the the module ! and you are trying to test if the module can initialize it's components , it should.

but i recommend you do this in e2e testing. in my opinion, in unit testing you should focus on testing the services or other components behaviors not the modules.

Upvotes: 4

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