单元测试HttpClientModule(Angular 4.3+)时出错 [英] Error while unit testing HttpClientModule (Angular 4.3+)

问题描述

我正在探索新的Angular HttpClientModule并遇到一个莫名其妙的错误.该模块足够新，我无法找到有关如何进行单元测试的任何有用信息，并且官方文档中没有任何示例.

I'm exploring the new Angular HttpClientModule and running into an inexplicable error. The module is new enough that I can't yet find any useful information about how to unit test, and the official documentation doesn't have any examples.

该应用程序包含一种方法的服务，该方法将URL传递给http.get.当我在浏览器上下文(又称为ng serve)中调用此方法时，http调用将正常执行.在单元测试的上下文中调用时，出现以下错误:

The app contains a service with one method, which passes a URL to http.get. When I call this method in a browser context (aka ng serve), the http call executes normally. When called in the context of a unit test, I get the following error:

TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.

这是使用Angular CLI生成的最小应用程序.以下是相关代码:

This is a minimal app generated with Angular CLI. Here's the pertinent code:

app.module.ts:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { HttpClientModule } from '@angular/common/http';
import { AppComponent } from './app.component';

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, HttpClientModule],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

app.component.ts:

import { Component, OnInit } from '@angular/core';
import { TestService } from './test.service'

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
  providers: [TestService]
})
export class AppComponent {
  title = 'app';

  constructor(private testSvc: TestService) {}

  ngOnInit() {
    this.testSvc.executeGet('http://www.example.com');
  }
}

test.service.ts:

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Injectable()
export class TestService {
  constructor(private http:HttpClient) {}

  executeGet(url:string) {
    this.http.get(url)
      .subscribe(
        data => console.log('success', data),
        error => console.log('error', error)
    );
  }
}

test.service.spec.ts:

import { HttpClient, HttpHandler } from '@angular/common/http';
import { TestBed, inject } from '@angular/core/testing';
import { TestService } from './test.service';

describe('TestService', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [HttpClient, HttpHandler, TestService]
    });
  });

  it('should executeGet', inject([TestService], (svc: TestService) => {
    expect(svc.executeGet).toBeDefined();
    // this is where the 'undefined' error occurs
    svc.executeGet('http://www.example.com'); 
  }));
});

任何指导或指针，我们将不胜感激.

Any guidance or pointers greatly appreciated.

推荐答案

缺少HttpClientModule的导入

Import of HttpClientModule missing

这是关于plnkr的有效示例

describe('TestService', () => {
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [HttpClientModule],
      providers: [TestService]
    });
  });

  it('should executeGet', () => {
    const testService = TestBed.get(TestService);

    expect(testService.executeGet).toBeDefined();
    testService.executeGet('http://www.example.com');
  }));
});

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