How to mock library?

[shawngustaw]

Is it correct that @nestjs-cognito/testing package still hits a live cognito service? If so is there a better way to mock the library entirely? This might be something nice to add to the docs 👍

[Lokicoule]

Hey @shawngustaw,

Thanks for the question. Yes, you're correct. The @nestjs-cognito/testing package is not intended to mock AWS Cognito. Instead, the CognitoTestingController provided by the package is used for e2e testing.

The CognitoTestingController exposes a single endpoint, /cognito-testing-login, which uses the HTTP POST method. This endpoint allows you to test the authentication process with AWS Cognito by sending a request with the username, password, and clientId in the request body. It handles the scenario where the user is not activated by default, making it useful for testing and verifying the behavior of AWS Cognito. It serves as a reference point and can help identify if the Cognito User Pool is misconfigured, as it has already been tested and is known to be working in a properly configured environment.

If you're looking for instructions on setting up the testing environment using @nestjs-cognito/testing, you can find more details in the wiki.

However, if you have a specific use case that requires mocking AWS Cognito, I guess you can easily achieve it using Jest.

Don't know if it's clear, but I hope that helps you to understand the goal behind this package ^^

[jpamdeth]

I am also having trouble mocking the dependencies injected by @nestjs-cognito/core. My service class has this constructor:

  constructor(private prisma: PrismaService,
              @InjectCognitoIdentityProvider()
              private readonly client: CognitoIdentityProvider) {}

My test has this:

  let identityService: IdentityService;
  let prismaService: DeepMocked<PrismaService>;
  let client: DeepMocked<CognitoIdentityProvider>;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [
        IdentityService,
        {
          provide: PrismaService,
          useValue: createMock<PrismaService>(),
        },
        {
          provide: CognitoIdentityProvider,
          useValue: createMock<CognitoIdentityProvider>(),
        }
      ],
    }).compile();

    identityService = module.get<IdentityService>(IdentityService);
    prismaService = module.get(PrismaService);
    client = module.get(CognitoIdentityProvider);
  });

But I'm getting an error that the dependencies are not satisfied:
Nest can't resolve dependencies of the IdentityService (PrismaService, ?). Please make sure that the argument "COGNITO_IDENTITY_PROVIDER_INSTANCE_TOKEN" at index [1] is available in the RootTestModule context.

Is it not possible to use the @InjectCognitoIdentityProvider() decorator and still inject the mock to satisfy the dependency?

[Lokicoule]

I guess you should replace the provided key with COGNITO_IDENTITY_PROVIDER_INSTANCE_TOKEN to make it works:

import { COGNITO_IDENTITY_PROVIDER_INSTANCE_TOKEN } from "@nestjs-cognito/core";

  let identityService: IdentityService;
  let prismaService: DeepMocked<PrismaService>;
  let client: DeepMocked<CognitoIdentityProvider>;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [
        IdentityService,
        {
          provide: PrismaService,
          useValue: createMock<PrismaService>(),
        },
        {
          provide: COGNITO_IDENTITY_PROVIDER_INSTANCE_TOKEN,
          useValue: createMock<CognitoIdentityProvider>(),
        }
      ],
    }).compile();

    identityService = module.get<IdentityService>(IdentityService);
    prismaService = module.get(PrismaService);
    client = module.get(CognitoIdentityProvider);
  });

[jpamdeth]

This version worked:

  let identityService: IdentityService;
  let prismaService: DeepMocked<PrismaService>;
  let client: DeepMocked<CognitoIdentityProvider>;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [
        IdentityService,
        {
          provide: PrismaService,
          useValue: createMock<PrismaService>(),
        },
        {
          provide: COGNITO_IDENTITY_PROVIDER_INSTANCE_TOKEN,
          useValue: createMock<CognitoIdentityProvider>(),
        }
      ],
    }).compile();

    identityService = module.get<IdentityService>(IdentityService);
    prismaService = module.get(PrismaService);
    client = module.get(COGNITO_IDENTITY_PROVIDER_INSTANCE_TOKEN);
  });