在 NestJS Jest 测试中覆盖提供者 [英] Overriding providers in NestJS Jest tests

问题描述

我想使用内存中的 Mongo 实例来模拟数据，以便在我的 NestJS 应用程序中进行测试.我有一个数据库提供程序，它使用 mongoose 连接到我的生产数据库，它是我的数据库模块的一部分，而后者又被导入到其他模块中.

I want to use an in-memory Mongo instance to mock data for testing purposes in my NestJS application. I have a database provider which connects to my production db using mongoose, which is part of my database module, which in turn gets imported into other modules.

我试图在我的 Jest 测试中覆盖数据库提供程序，以便我可以使用内存中的 Mongo 实例.

I am trying to override the database provider within my Jest tests so I can use the in-memory Mongo instance.

这是数据库模块:

import { Module } from '@nestjs/common';
import { databaseProviders } from './database.providers';

@Module({
  providers: [...databaseProviders],
  exports: [...databaseProviders],
})
export class DatabaseModule { }

和数据库提供者:

export const databaseProviders = [
  {
    provide: 'DbConnectionToken',
    useFactory: async (): Promise<typeof mongoose> =>
      await mongoose.connect(PRODUCTION_DATABASE_URL),
  },
];

我有一个事件模块，它从数据库模块导入和使用数据库连接，事件服务是我正在测试的 - 我的 events.spec.ts 中的 beforeEach:

I have an Events module which imports and uses the database connection from the database module the Events service is what I am testing - the beforeEach in my events.spec.ts:

beforeEach(async () => {
    const module = await Test.createTestingModule({
      imports: [EventsModule],
      providers: [
        EventsService,
        {
          provide: 'EventModelToken',
          useValue: EventSchema
        },
      ],
    }).compile();

    eventService = module.get<EventsService>(EventsService);
  });

我尝试将 DatabaseModule 导入测试模块，然后添加我的自定义提供程序，假设它会覆盖数据库提供程序，但它没有按我预期的那样工作，所以我担心我可能会误解覆盖提供程序在这种情况下的工作方式.

I tried importing the DatabaseModule into the testing module and then adding my custom provider assuming it would override the database provider, but it doesn't work as I expected so I fear I may misunderstand how overriding providers works in this context.

这是我试过的:

beforeEach(async () => {
  const module = await Test.createTestingModule({
    imports: [EventsModule, DatabaseModule],
    providers: [
      EventsService,
      {
        provide: 'EventModelToken',
        useValue: EventSchema
      },
      {
        provide: 'DbConnectionToken',
        useFactory: async (): Promise<typeof mongoose> =>
          await mongoose.connect(IN_MEMORY_DB_URI),
      },
    ],
  }).compile();

  eventService = module.get<EventsService>(EventsService);
});

推荐答案

如文档中所述 https://docs.nestjs.com/fundamentals/unit-testing 您可以使用值、工厂或类覆盖提供程序.

As specified in the docs https://docs.nestjs.com/fundamentals/unit-testing you can override the provider with a value, factory or class.

beforeEach(async () => {
    const module = await Test.createTestingModule({
        imports: [EventsModule, DatabaseModule],
        providers: [
            EventsService,
        ],
    }).overrideProvider('DbConnectionToken')
    .useFactory({
        factory: async (): Promise<typeof mongoose> =>
          await mongoose.connect(IN_MEMORY_DB_URI),
    })
    .compile();

    eventService = module.get<EventsService>(EventsService);
});

另一种方法是为您的配置创建一个提供程序 :) 像这样！

An alternative would be to make a provider for your configs :) Like so!

@Module({})
export DatabaseModule {
    public static forRoot(options: DatabaseOptions): DynamicModule {
        return {
            providers: [
                {
                    provide: 'DB_OPTIONS',
                    useValue: options,
                },
                {
                    provide: 'DbConnectionToken',
                    useFactory: async (options): Promise<typeof mongoose> => await mongoose.connect(options),
                    inject: ['DB_OPTIONS']
                },
            ],
        };
    }
}

然后像这样使用

const module: TestingModule = await Test.createTestingModule({
    imports: [DatabaseModule.forRoot({ host: 'whatever'})],
});

现在您可以随时随地更改选项:)

Now you're able to change the options wherever you're using it :)

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