node.js - 如何开 Jest 模拟 Nestjs 导入？

Question

我想为我的 Nestjs“类(class)”存储库服务(依赖于 Mongoose 模型和 Redis 的服务)编写单元测试。

类(class).repository.ts:

    import { Injectable, HttpException, NotFoundException } from "@nestjs/common";
    import { InjectModel } from "@nestjs/mongoose"
    import { Course } from "../../../../shared/course";
    import { Model } from "mongoose";
    import { RedisService } from 'nestjs-redis';


    @Injectable({}) 
    export class CoursesRepository {

      private redisClient;
      constructor(
        @InjectModel('Course') private courseModel: Model<Course>,
        private readonly redisService: RedisService,
      ) {
        this.redisClient = this.redisService.getClient();

      }


      async findAll(): Promise<Course[]> {
        const courses = await this.redisClient.get('allCourses');
        if (!courses) {
          console.log('return from DB');
          const mongoCourses = await this.courseModel.find();
          await this.redisClient.set('allCourses', JSON.stringify(mongoCourses), 'EX', 20);
          return mongoCourses;
        }

        console.log('return from cache');
        return JSON.parse(courses);
      }
}

测试是这样初始化的:

beforeEach(async () => {
  const moduleRef = await Test.createTestingModule({
    imports: [
      MongooseModule.forRoot(MONGO_CONNECTION,  { 
        useNewUrlParser: true,
        useUnifiedTopology: true
      }),
      MongooseModule.forFeature([
        { name: "Course", schema: CoursesSchema },
        { name: "Lesson", schema: LessonsSchema }
      ]),
      RedisModule.register({})
    ],
      controllers: [CoursesController, LessonsController],
      providers: [
         CoursesRepository,
         LessonsRepository
        ],
    }).compile();

  coursesRepository = moduleRef.get<CoursesRepository>(CoursesRepository);
  redisClient = moduleRef.get<RedisModule>(RedisModule);

});

我的类(class)存储库服务有 2 个依赖项 - Redis 和 Mongoose 模型(类(class))。我想 mock 他们俩。

如果我 mock 一个提供者，我会使用该语法:

providers: [
    {provide: CoursesRepository, useFactory: mockCoursesRepository},
     LessonsRepository
    ],

我可以创建一个模拟 Redis 服务来代替测试期间的实际 Redis 服务吗？

如何？

谢谢，亚龙

Answer 1

请注意，接受的答案模拟了一个提供程序，如果它也是由 TestingModule 与提供程序一起提供的，则它将满足被测类的依赖关系。然而，它并没有按照要求模拟导入，这可能是不同的。例如。如果您需要导入某个也依赖于模拟值的模块，则这将不起作用:

// DOES NOT WORK
const module = await Test.createTestingModule({
  imports: [
    ModuleThatNeedsConfig,
  ],
  providers: [
    { provide: ConfigService, useValue: mockConfig },
    ExampleService, // relies on something from ModuleThatNeedsConfig
  ]
}).compile();

要模拟导入，您可以使用导出模拟值的DynamicModule:

const module = await Test.createTestingModule({
  imports: [
    {
      module: class FakeModule {},
      providers: [{ provide: ConfigService, useValue: mockConfig }],
      exports: [ConfigService],
    },
    ModuleThatNeedsConfig,
  ],
  providers: [
    ClassUnderTest,
  ]
}).compile();

由于这有点冗长，像这样的实用函数可能会有所帮助:

export const createMockModule = (providers: Provider[]): DynamicModule => {
  const exports = providers.map((provider) => (provider as any).provide || provider);
  return {
    module: class MockModule {},
    providers,
    exports,
    global: true,
  };
};

然后可以这样使用:

const module = await Test.createTestingModule({
  imports: [
    createMockModule([{ provide: ConfigService, useValue: mockConfig }]),
    ModuleThatNeedsConfig,
  ],
  providers: [
    ClassUnderTest,
  ]
}).compile();

这通常具有额外的好处，可以让您导入被测类的模块，而不是让测试绕过模块并直接提供值。

const module = await Test.createTestingModule({
  imports: [
    createMockModule([{ provide: ConfigService, useValue: mockConfig }]),
    ModuleThatNeedsConfig,
    ModuleUnderTest,
  ],
}).compile();

const service = module.get(ClassUnderTest);