SpyOn TypeORM repository to change the return value for unit testing NestJS

问题

I would like to unittest corner cases for my TypeORM database calls. I have already mocked all my TypeORM repositories with valid data. But I would like to SpyOn the repository and change the return value form TypeORM. How do I do that?

import {INestApplication} from '@nestjs/common';
import {Test} from '@nestjs/testing';
import {CommonModule} from '@src/common/common.module';
import {AuthService} from './auth.service';
import {Repository} from 'typeorm';
import {V3User} from '@src/database/entity/user.v3entity';

describe('AuthService', () => {
    let service: AuthService;
    let app: INestApplication;

    beforeEach(async () => {
        const module = await Test.createTestingModule({
            imports: [CommonModule.forRoot(`${process.env.DEV_ENV}`)],
            providers: [AuthService,     
                 {provide: 'V3USER_REPOSITORY', useValue: mockRepositoryV3User()},
           ],
        }).compile();

        app = module.createNestApplication();
        await app.init();

        service = module.get<AuthService>(AuthService);
    });



    it('test auth service - with non existing user in v3 db', async () => {

        jest.spyOn(?????? , 'findOne').mockImplementation(() => undefined);

        const res = await service.loginUser("bad token");

        await expect(service.tokenBasedAuth('example bad token'))
        .rejects.toThrow('bad token exception');
    });
});

I mock the database like this for normal test cases:

export const mockRepositoryV3User = () => ({
    metadata: {
        columns: [],
        relations: [],
    },
    findOne: async () =>
        Promise.resolve({
            id: 3,
            email: 'email@example.com',
            first_name: 'david',
            last_name: 'david',
            last_login: '2019-07-15',
            date_joined: '2019-07-15',
        }),
});

回答1:

Okay, after finally getting around to testing and playing with ideas I've found that this is a valid strategy

Assume we have set up a PhotoEntity with basic properties, nothing too special (id, name, description, etc.)

import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';

@Entity()
export class Photo {
  @PrimaryGeneratedColumn()
  id: number;

  @Column({ length: 500 })
  name: string;

  @Column('text')
  description: string;

  @Column()
  filename: string;

  @Column('int')
  views: number;

  @Column()
  isPublished: boolean;
}

Set up a PhotoService such as the following (super basic but it will illustrate the point):

import { Injectable } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { Photo } from './photo.entity';

@Injectable()
export class PhotoService {
  constructor(
    @InjectRepository(Photo)
    private readonly photoRepository: Repository<Photo>,
  ) {}

  async findAll(): Promise<Photo[]> {
    return await this.photoRepository.find();
  }
}

We can useClass: Repository so that we don't have to do any of the heavy lifting of setting up a repository class to use for testing (Repository is imported from the TypeORM package. We can then get the repo from the module and save it to a value for easy mocking and set up our tests like so:

import { Test, TestingModule } from '@nestjs/testing';
import { PhotoService } from './photo.service';
import { getRepositoryToken } from '@nestjs/typeorm';
import { Photo } from './photo.entity';
import { Repository } from 'typeorm';

describe('PhotoService', () => {
  let service: PhotoService;
  // declaring the repo variable for easy access later
  let repo: Repository<Photo>;

  beforeEach(async () => {
    const module: TestingModule = await Test.createTestingModule({
      providers: [
        PhotoService,
        {
          // how you provide the injection token in a test instance
          provide: getRepositoryToken(Photo),
          // as a class value, Repository needs no generics
          useClass: Repository,
        },
      ],
    }).compile();

    service = module.get<PhotoService>(PhotoService);
    // Save the instance of the repository and set the correct generics
    repo = module.get<Repository<Photo>>(getRepositoryToken(Photo));
  });

  it('should be defined', () => {
    expect(service).toBeDefined();
  });

  it('should return for findAll', async () => {
    // mock file for reuse
    const testPhoto: Photo =  {
      id: 'a47ecdc2-77d6-462f-9045-c440c5e4616f',
      name: 'hello',
      description: 'the description',
      isPublished: true,
      filename: 'testFile.png',
      views: 5,
    };
    // notice we are pulling the repo variable and using jest.spyOn with no issues
    jest.spyOn(repo, 'find').mockResolvedValueOnce([testPhoto]);
    expect(await service.findAll()).toEqual([testPhoto]);
  });
});

Run your tests against the specified file or against all tests

▶ npm run test -- photo.service

> nestjs-playground@0.0.1 test ~/Documents/code/nestjs-playground
> jest "photo.service"

 PASS  src/photo/photo.service.spec.ts
  PhotoService
    ✓ should be defined (17ms)
    ✓ should return for findAll (4ms)  < -- test passes with no problem

Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        3.372s, estimated 4s
Ran all test suites matching /photo.service/i.

来源：https://stackoverflow.com/questions/57099863/spyon-typeorm-repository-to-change-the-return-value-for-unit-testing-nestjs

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nestjs

typeorm