How to mock Jest Redis in Nestjs - node.js

Question

I'm working on NestJs application and wrote unit test for my authenticateUser function in user.service.ts.It's has pass in my local machine.but when I deployed it in to server and run unit test, i got an error Redis connection to 127.0.0.1:6379 failed - connect ECONNREFUSED.Seems like redis mock is not working.How should I mock redis and resolve this issue for working?
user.service.ts
async authenticateUser(authDto: AuthDTO): Promise<AuthResponse> {
try {
const userData = await this.userRepository.findOne({msisdn});
if(userData){
await this.redisCacheService.setCache(msisdn, userData);
}
} catch (error) {
console.log(error)
}
}
redisCache.service.ts
export class RedisCacheService {
constructor(
#Inject(CACHE_MANAGER) private readonly cache: Cache,
) {}
async setCache(key, value) {
await this.cache.set(key, value);
}
}
user.service.spec.ts
describe('Test User Service', () => {
let userRepository: Repository<UserEntity>;
let userService: UserService;
let redisCacheService: RedisCacheService;
let cacheManager: any;
beforeEach(async () => {
const module: TestingModule = await Test.createTestingModule({
providers: [
UserService,
UserEntity,
RedisCacheService,
{
provide: getRepositoryToken(UserEntity),
useClass: registeredApplicationRepositoryMockFactory,
},
],
imports: [CacheModule.register({})],
}).compile();
userService = module.get<UserService>(UserService);
userRepository = module.get<Repository<UserEntity>>(
getRepositoryToken(UserEntity),
);
redisCacheService = module.get<RedisCacheService>(RedisCacheService);
cacheManager = module.get<any>(CACHE_MANAGER);
});
it('authenticateUser should return success response', async () => {
const userEntity = { id: 1, name: 'abc', age: 25 };
const mockSuccessResponse = new AuthResponse(
HttpStatus.OK,
STRING.SUCCESS,
`${STRING.USER} ${STRING.AUTHENTICATE} ${STRING.SUCCESS}`,
{},
);
jest.spyOn(userRepository, 'findOne').mockResolvedValueOnce(userEntity);
jest.spyOn(redisCacheService, 'setCache').mockResolvedValueOnce(null);
expect(await userService.authenticateUser(mockAuthBody)).toEqual(mockSuccessResponse);
});
});

Answer 1

You can mock CACHE_MANAGER using a custom provider:
import { CACHE_MANAGER } from '#nestjs/common';
import { Cache } from 'cache-manager';
describe('AppService', () => {
let service: AppService;
let cache: Cache;
beforeEach(async () => {
const app = await Test.createTestingModule({
providers: [
AppService,
{
provide: CACHE_MANAGER,
useValue: {
get: () => 'any value',
set: () => jest.fn(),
},
},
],
})
.compile();
service = app.get<AppService>(AppService);
cache = app.get(CACHE_MANAGER);
});
// Then you can use jest.spyOn() to spy and mock
it(`should cache the value`, async () => {
const spy = jest.spyOn(cache, 'set');
await service.cacheSomething();
expect(spy).toHaveBeenCalledTimes(1);
expect(spy.mock.calls[0][0]).toEqual('key');
expect(spy.mock.calls[0][1]).toEqual('value');
});
it(`should get the value from cache`, async () => {
const spy = jest.spyOn(cache, 'get');
await service.getSomething();
expect(spy).toHaveBeenCalledTimes(1);
});
it(`should return the value from the cache`, async () => {
jest.spyOn(cache, 'get').mockResolvedValueOnce('value');
const res = await service.getSomething();
expect(res).toEqual('value');
}),
});
More details on Custom Providers: https://docs.nestjs.com/fundamentals/custom-providers
Two more things, for unit testing you shouldn't import modules but mock the dependencies instead. And as Daniel said, UserService is not using CACHE_MANAGER but RedisCacheService, so you should mock RedisCacheService.
Usually the best thing to do is to only provide the service you're testing and mock the dependencies.

Answer 2

in order to use the jest spy functions you need to return the jest function directly.
providers: [
AppService,
{
provide: CACHE_MANAGER,
useValue: {
get: () => 'any value',
set: jest.fn(),
},
},
],