如何使用Jest和NestJS模拟注入存储库?

在NestJS项目中,使用Jest测试服务案例。我创建了一个find方法,并在解析器(GraphQL)函数中使用它。在测试解析器时,它在服务中找不到find方法。

src/serivce/post.ts

    import { Injectable } from '@nestjs/common';
    import { InjectRepository } from '@nestjs/typeorm';

    import { AbstractPostRepository } from '@abstractRepository/AbstractPostRepository';
    import { PostRepository } from '@repository/PostRepository';

    @Injectable()
    export class PostService {
      constructor(
        @InjectRepository(PostRepository)
        private postRepo: AbstractPostRepository,
      ) {}

      async findById(id: string) {
        const posts = await this.postRepo.findById(id);

        ......
        return posts;
      }
    }

src/resolver/query/post.ts

    import { Args, Query, Resolver } from '@nestjs/graphql';

    import { Authorized } from '@lib/auth/authorized';
    import { PermissionScope } from '@lib/auth/permissionScope';
    import { PostService } from '@service/postService';

    @Resolver()
    export class PostsResolver {
      constructor(private postService: PostService) {}

      @PermissionScope()
      @Authorized([
        PermissionEnum.READ_MANAGEMENT,
      ])
      @Query()
      async findPosts() {
         return await this.postService.findById(id);
      }
    }

与此服务相关的解析器的单元测试:

测试/单元/解析器/post.spec.ts

    import { Test, TestingModule } from '@nestjs/testing';

    import { PERMISSION_MANAGER } from '@lib/auth/permissionManager.module';
    import { PostsResolver } from '@resolver/query/post';
    import { PostService } from '@service/postService';

    describe('PostsResolver', () => {
      let resolver: PostsResolver;

      beforeEach(async () => {
        const module: TestingModule = await Test.createTestingModule({
          providers: [
            PostsResolver,
            {
              provide: PERMISSION_MANAGER,
              useValue: jest.fn(),
            },
            {
              provide: PostService,
              useFactory: () => ({
                findById: jest.fn(() => [
                  {
                    id: '11111111-1111-1111-1111-111111111111',
                    name: 'name1',
                  },
                ]),
              }),
            },
          ],
        }).compile();

        resolver = module.get<PostsResolver>(PostsResolver);
      });

      describe('findPosts', () => {
        it('should return data', async () => {
          const posts = await resolver.findPosts({
            id: '11111111-1111-1111-1111-111111111111',
          });

          const expected = [
            {
              id: '11111111-1111-1111-1111-111111111111',
              name: 'name1',
            },
          ];

          expect(posts).toEqual(expected);
        });
      });
    });

运行此测试时出现错误:

  ● PostsResolver › findPosts › should return data

    TypeError: Cannot read properties of undefined (reading 'findById')

      22 |     { id }: FindPostsInput,
      23 |   ) {
    > 24 |     return await this.postService.findById(
         |                                         ^
      25 |       id,
      26 |     );

      at PostsResolver.findPosts (src/resolver/query/post.ts:24:41)
      at Object.<anonymous> (test/unit/resolver/post.spec.ts:59:42)

这似乎是模拟服务 findById 在中 Test.createTestingModule 不起作用。如何正确地模仿?是否与某些注射原因有关?