How to mock chained function calls using jest? - node.js

Question

I am testing the following service:
#Injectable()
export class TripService {
private readonly logger = new Logger('TripService');
constructor(
#InjectRepository(TripEntity)
private tripRepository: Repository<TripEntity>
) {}
public async showTrip(clientId: string, tripId: string): Promise<Partial<TripEntity>> {
const trip = await this.tripRepository
.createQueryBuilder('trips')
.innerJoinAndSelect('trips.driver', 'driver', 'driver.clientId = :clientId', { clientId })
.where({ id: tripId })
.select([
'trips.id',
'trips.distance',
'trips.sourceAddress',
'trips.destinationAddress',
'trips.startTime',
'trips.endTime',
'trips.createdAt'
])
.getOne();
if (!trip) {
throw new HttpException('Trip not found', HttpStatus.NOT_FOUND);
}
return trip;
}
}
My repository mock:
export const repositoryMockFactory: () => MockType<Repository<any>> = jest.fn(() => ({
findOne: jest.fn(entity => entity),
findAndCount: jest.fn(entity => entity),
create: jest.fn(entity => entity),
save: jest.fn(entity => entity),
update: jest.fn(entity => entity),
delete: jest.fn(entity => entity),
createQueryBuilder: jest.fn(() => ({
delete: jest.fn().mockReturnThis(),
innerJoinAndSelect: jest.fn().mockReturnThis(),
innerJoin: jest.fn().mockReturnThis(),
from: jest.fn().mockReturnThis(),
where: jest.fn().mockReturnThis(),
execute: jest.fn().mockReturnThis(),
getOne: jest.fn().mockReturnThis(),
})),
}));
My tripService.spec.ts:
import { Test, TestingModule } from '#nestjs/testing';
import { TripService } from './trip.service';
import { MockType } from '../mock/mock.type';
import { Repository } from 'typeorm';
import { TripEntity } from './trip.entity';
import { getRepositoryToken } from '#nestjs/typeorm';
import { repositoryMockFactory } from '../mock/repositoryMock.factory';
import { DriverEntity } from '../driver/driver.entity';
import { plainToClass } from 'class-transformer';
describe('TripService', () => {
let service: TripService;
let tripRepositoryMock: MockType<Repository<TripEntity>>;
let driverRepositoryMock: MockType<Repository<DriverEntity>>;
beforeEach(async () => {
const module: TestingModule = await Test.createTestingModule({
providers: [
TripService,
{ provide: getRepositoryToken(DriverEntity), useFactory: repositoryMockFactory },
{ provide: getRepositoryToken(TripEntity), useFactory: repositoryMockFactory },
],
}).compile();
service = module.get<TripService>(TripService);
driverRepositoryMock = module.get(getRepositoryToken(DriverEntity));
tripRepositoryMock = module.get(getRepositoryToken(TripEntity));
});
it('should be defined', () => {
expect(service).toBeDefined();
expect(driverRepositoryMock).toBeDefined();
expect(tripRepositoryMock).toBeDefined();
});
describe('TripService.showTrip()', () => {
const trip: TripEntity = plainToClass(TripEntity, {
id: 'one',
distance: 123,
sourceAddress: 'one',
destinationAddress: 'one',
startTime: 'one',
endTime: 'one',
createdAt: 'one',
});
it('should show the trip is it exists', async () => {
tripRepositoryMock.createQueryBuilder.mockReturnValue(trip);
await expect(service.showTrip('one', 'one')).resolves.toEqual(trip);
});
});
});
I want to mock the call to the tripRepository.createQueryBuilder().innerJoinAndSelect().where().select().getOne();
First question, should I mock the chained calls here because I assume that it should already be tested in Typeorm.
Second, if I want to mock the parameters passed to each chained call and finally also mock the return value, how can I go about it?

Answer 1

I had a similar need and solved using the following approach.
This is the code I was trying to test. Pay attention to the createQueryBuilder and all the nested methods I called.
const reactions = await this.reactionEntity
.createQueryBuilder(TABLE_REACTIONS)
.select('reaction')
.addSelect('COUNT(1) as count')
.groupBy('content_id, source, reaction')
.where(`content_id = :contentId AND source = :source`, {
contentId,
source,
})
.getRawMany<GetContentReactionsResult>();
return reactions;
Now, take a look at the test I wrote that simulates the chained calls of the above methods.
it('should return the reactions that match the supplied parameters', async () => {
const PARAMS = { contentId: '1', source: 'anything' };
const FILTERED_REACTIONS = REACTIONS.filter(
r => r.contentId === PARAMS.contentId && r.source === PARAMS.source,
);
// Pay attention to this part. Here I created a createQueryBuilder
// const with all methods I call in the code above. Notice that I return
// the same `createQueryBuilder` in all the properties/methods it has
// except in the last one that is the one that return the data
// I want to check.
const createQueryBuilder: any = {
select: () => createQueryBuilder,
addSelect: () => createQueryBuilder,
groupBy: () => createQueryBuilder,
where: () => createQueryBuilder,
getRawMany: () => FILTERED_REACTIONS,
};
jest
.spyOn(reactionEntity, 'createQueryBuilder')
.mockImplementation(() => createQueryBuilder);
await expect(query.getContentReactions(PARAMS)).resolves.toEqual(
FILTERED_REACTIONS,
);
});

Answer 2

Guilherme's answer is totally right. I just wanted to offer a modified approach that might apply to more test cases, and in TypeScript. Instead of defining your chained calls as (), you can use a jest.fn, allowing you to make more assertions. e.g.,
/* eslint-disable #typescript-eslint/no-explicit-any */
const createQueryBuilder: any = {
select: jest.fn().mockImplementation(() => {
return createQueryBuilder
}),
addSelect: jest.fn().mockImplementation(() => {
return createQueryBuilder
}),
groupBy: jest.fn().mockImplementation(() => {
return createQueryBuilder
}),
where: jest.fn().mockImplementation(() => {
return createQueryBuilder
}),
getRawMany: jest
.fn()
.mockImplementationOnce(() => {
return FILTERED_REACTIONS
})
.mockImplementationOnce(() => {
return SOMETHING_ELSE
}),
}
/* run your code */
// then you can include an assertion like this:
expect(createQueryBuilder.groupBy).toHaveBeenCalledWith(`some group`)

Answer 3

The solution I found to work in my case was to
create a repository class, add your custom query to the class
#EntityRepository(User)
export class UserRepository extends Repository<User> {
async getStatus(id: string) {
const status = await this.createQueryBuilder()
.select('User.id')
.where('User.id = :id', { id })
.getRawOne();
return {status};
}
}
mock the new repository class using 'jest-mock-extended' and 'jest-when' dependencies. This way you only need to mock the UserRepository and not all it's nested queries.
Now you can define the behaviour of the repository to resolve a predefined object (in my case a Partial object).
// some file where I need to call getStatus() in a test
const userRepoMock = mock<UserRepository>()
// lines omitted
const user = {
status: open,
};
when(userRepoMock.getStatus).mockResolvedValue(user as User);
// assert status