使用NestJS与Node测试运行器时E2E测试依赖注入失效问题

问题背景 #

使用NestJS和Node测试运行器搭建新项目时，单元测试可正常执行，但E2E测试抛出TypeError: Cannot read properties of undefined (reading 'getHello')错误。服务启动后可正常运行，仅E2E测试阶段出现依赖注入异常。

相关代码片段 #

Controller代码

import { Controller, Get } from '@nestjs/common';
import { AppService } from './app.service';

@Controller()
export class AppController {
  constructor(private readonly appService: AppService) {
    console.log(appService)
  }

  @Get()
  getHello(): string {
    return this.appService.getHello();
  }
}

Service代码

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

@Injectable()
export class AppService {
  getHello(): string {
    return 'Hello World!';
  }
}

Module代码

import { Module } from '@nestjs/common';
import { AppController } from './app.controller';
import { AppService } from './app.service';

@Module({
  imports: [],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

E2E测试代码

import { Test } from '@nestjs/testing';
import test from 'node:test';
import request from 'supertest';
import { INestApplication } from "@nestjs/common";
import * as assert from "assert";
import { AppModule } from "src/demo/app.module";

test.describe('AppController.getHello', () => {
  let app: INestApplication;

  test.before(async () => {
    const moduleFixture = await Test.createTestingModule({
      imports: [AppModule],
    }).compile();

    app = moduleFixture.createNestApplication();
    await app.init();
  });
  test.after(async () => {
    await app.close();
  })

  test.it('should return "Hello World!"', async () => {
    await request(app.getHttpServer())
        .get('/')
        .then((response) => assert.strictEqual(response.body, 'Hello World!'))
  });
});

错误信息 #

执行测试命令glob ./**/*.test.ts -c 'tsx --test'时触发错误：

TypeError: Cannot read properties of undefined (reading 'getHello')
    at AppController.getHello (.../app.controller.ts:12:28)

解决思路 #

• 调整测试钩子的异步逻辑：Node内置test模块的before钩子可能未正确等待NestJS测试模块初始化完成，替换为beforeEach确保每次测试前都完成模块初始化：

  test.beforeEach(async () => {
    const moduleFixture = await Test.createTestingModule({
      imports: [AppModule],
    }).compile();
  
    app = moduleFixture.createNestApplication();
    await app.init();
  });
  

• 验证依赖注入容器状态：在测试模块编译后，手动检查容器中的服务实例是否存在，确认依赖注入流程正常：

  test.before(async () => {
    const moduleFixture = await Test.createTestingModule({
      imports: [AppModule],
    }).compile();
    
    // 打印服务实例，确认是否被正确注册
    const appService = moduleFixture.get(AppService);
    console.log('AppService instance:', appService);
  
    app = moduleFixture.createNestApplication();
    await app.init();
  });
  

• 优化测试命令的文件匹配规则：避免glob命令同时匹配单元测试和E2E测试文件导致路径冲突，指定仅运行E2E测试文件：

  glob ./**/*.e2e-test.ts -c 'tsx --test'
  

  建议将E2E测试文件统一命名为*.e2e.test.ts，与单元测试文件区分开。

• 检查模块导入路径：确认测试文件中AppModule的导入路径正确，避免相对路径错误导致模块未被加载：

  // 替换为项目中实际的相对路径
  import { AppModule } from '../app.module';
  

• 升级NestJS版本：部分旧版本NestJS与Node内置测试模块存在兼容性问题，升级到最新稳定版本可解决此类问题：

  npm install @nestjs/core@latest @nestjs/common@latest @nestjs/testing@latest
  

内容的提问来源于stack exchange，提问作者Charlie Camus