Angular 18+Jest测试：注入HttpClient时无法解析DummyTest参数

我正将测试从Jasmine/Karma迁移至Jest，在注入HttpClient及其测试控制器时遇到困难。按照Angular官方Http测试指南编写了如下测试代码：

import { HttpClient, provideHttpClient } from '@angular/common/http';
import { HttpTestingController, provideHttpClientTesting } from '@angular/common/http/testing';
import { TestBed } from '@angular/core/testing';

describe('Testings tests', () => {
  let httpTestingController!: HttpTestingController;
  let dummyTest: DummyTest;
  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [DummyTest, provideHttpClient(), provideHttpClientTesting()],
    });
    httpTestingController = TestBed.inject(HttpTestingController);
    dummyTest = TestBed.inject(DummyTest);
  });

  fit('Should request data', async () => {
    const promise = dummyTest.TestRequest();

    httpTestingController.expectOne('https://google.com').flush({});

    await promise;
  });
});

export class DummyTest {
  constructor(private httpClient: HttpClient) {}

  async TestRequest() {
    await this.httpClient.get('https://google.com');
  }
}

运行测试时出现以下错误：

NG0204: Can't resolve all parameters for DummyTest: (?).

  10 |       providers: [DummyTest, provideHttpClient(), provideHttpClientTesting()],
  11 |     });
> 12 |     httpTestingController = TestBed.inject(HttpTestingController);
     |                                     ^
  13 |     dummyTest = TestBed.inject(DummyTest);
  14 |   });

使用的是Angular 18和最新版本的Jest，已提供HttpClient和HttpClientTesting相关依赖，不清楚遗漏了什么。

• 错误核心原因：Angular 18默认启用Ivy严格注入模式，所有需要依赖注入的类必须显式添加@Injectable()装饰器，否则DI系统无法解析构造函数参数。
• 修复步骤：
  1. 导入Injectable装饰器：

     import { Injectable } from '@angular/core';
     

  2. 给DummyTest类添加@Injectable()装饰器：

     @Injectable()
     export class DummyTest {
       constructor(private httpClient: HttpClient) {}
     
       async TestRequest() {
         await this.httpClient.get('https://google.com');
       }
     }
     

• 补充说明：在旧版本Angular或非严格模式下，未添加@Injectable()的类可能被DI系统兼容解析，但Angular 18的严格模式强制要求显式声明，这也是Jest环境下触发错误的关键（Jest通常采用更严格的编译配置）。

内容的提问来源于stack exchange，提问作者J4N