使用TypeORM和Nestjs进行测试的过程,以及使用mock的jest?

我正在学习更多关于测试的知识,但是我一直在学习如何正确地执行涉及数据库的测试。

    import { IsAlphanumeric, IsEmail, MinLength } from 'class-validator';
    import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';
    @Entity()
    export class User {
      @PrimaryGeneratedColumn()
      public id!: number;

      @Column()
      public name!: string;

      @IsEmail()
      @Column()
      public email!: string;

      @MinLength(8)
      @Column()
      public password!: string;
    }

我有一个UserService,为实体注入存储库。

    import { Injectable } from '@nestjs/common';
    import { InjectRepository } from '@nestjs/typeorm';
    import { validateOrReject } from 'class-validator';
    import { Repository } from 'typeorm';
    import { CreateUserDTO } from './dto/create-user.dto';
    import { User } from './user.entity';

    @Injectable()
    export class UserService {
      constructor(
        @InjectRepository(User) private readonly userRepository: Repository<User>
      ) {}

      public async create(dto: CreateUserDTO) {
        const user = this.userRepository.create(dto);
        await validateOrReject(user);
        await this.userRepository.save(user);
      }

      public async findAll(): Promise<User[]> {
        return await this.userRepository.find();
      }

      public async findByEmail(email: string): Promise<User | undefined> {
        return await this.userRepository.findOne({
          where: {
            email,
          },
        });
      }
    }

这是我的初步测试,所以你可以按照我的思路。。。

    import { Test, TestingModule } from '@nestjs/testing';
    import { getRepositoryToken } from '@nestjs/typeorm';
    import { User } from './user.entity';
    import { UserService } from './user.service';

    const createMock = jest.fn((dto: any) => {
      return dto;
    });

    const saveMock = jest.fn((dto: any) => {
      return dto;
    });

    const MockRepository = jest.fn().mockImplementation(() => {
      return {
        create: createMock,
        save: saveMock,
      };
    });
    const mockRepository = new MockRepository();

    describe('UserService', () => {
      let service: UserService;

      beforeAll(async () => {
        const module: TestingModule = await Test.createTestingModule({
          providers: [
            UserService,
            {
              provide: getRepositoryToken(User),
              useValue: mockRepository,
            },
          ],
        }).compile();
        service = module.get<UserService>(UserService);
      });

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

      it('should not create invalid user', async () => {
        // ??
      });
    });

所以,虽然我可以做测试运行和一切,我不知道我实际上应该测试什么。很明显,我可以在create上测试它是否有效,对于findAll之类的其他东西,我觉得我只是在嘲笑数据库?为了正确地测试这个,是否需要将它连接到数据库,以便检查返回的数据是否正确?

测试功能?因为虽然我可以模拟save返回一个值,但我并不是在测试唯一列、可为null的数据、要设置的递增值等可能出现的任何错误。。。正确的?