Angular 2 Testing an Angular 2 App Testing Http Service
Example
Usually, services call remote Api to retrieve/send data. But unit tests shouldn't do network calls. Angular internally uses XHRBackend class to do http requests. User can override this to change behavior. Angular testing module provides MockBackend and MockConnection classes which can be used to test and assert http requests.
posts.service.ts
This service hits an api endpoint to fetch list of posts.
import { Http } from '@angular/http';
import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/rx';
import 'rxjs/add/operator/map';
export interface IPost {
userId: number;
id: number;
title: string;
body: string;
}
@Injectable()
export class PostsService {
posts: IPost[];
private postsUri = 'http://jsonplaceholder.typicode.com/posts';
constructor(private http: Http) {
}
get(): Observable<IPost[]> {
return this.http.get(this.postsUri)
.map((response) => response.json());
}
}
posts.service.spec.ts
Here, we will test above service by mocking http api calls.
import { TestBed, inject, fakeAsync } from '@angular/core/testing';
import {
HttpModule,
XHRBackend,
ResponseOptions,
Response,
RequestMethod
} from '@angular/http';
import {
MockBackend,
MockConnection
} from '@angular/http/testing';
import { PostsService } from './posts.service';
describe('PostsService', () => {
// Mock http response
const mockResponse = [
{
'userId': 1,
'id': 1,
'title': 'sunt aut facere repellat provident occaecati excepturi optio reprehenderit',
'body': 'quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto'
},
{
'userId': 1,
'id': 2,
'title': 'qui est esse',
'body': 'est rerum tempore vitae\nsequi sint nihil reprehenderit dolor beatae ea dolores neque\nfugiat blanditiis voluptate porro vel nihil molestiae ut reiciendis\nqui aperiam non debitis possimus qui neque nisi nulla'
},
{
'userId': 1,
'id': 3,
'title': 'ea molestias quasi exercitationem repellat qui ipsa sit aut',
'body': 'et iusto sed quo iure\nvoluptatem occaecati omnis eligendi aut ad\nvoluptatem doloribus vel accusantium quis pariatur\nmolestiae porro eius odio et labore et velit aut'
},
{
'userId': 1,
'id': 4,
'title': 'eum et est occaecati',
'body': 'ullam et saepe reiciendis voluptatem adipisci\nsit amet autem assumenda provident rerum culpa\nquis hic commodi nesciunt rem tenetur doloremque ipsam iure\nquis sunt voluptatem rerum illo velit'
}
];
beforeEach(() => {
TestBed.configureTestingModule({
imports: [HttpModule],
providers: [
{
provide: XHRBackend,
// This provides mocked XHR backend
useClass: MockBackend
},
PostsService
]
});
});
it('should return posts retrieved from Api', fakeAsync(
inject([XHRBackend, PostsService],
(mockBackend, postsService) => {
mockBackend.connections.subscribe(
(connection: MockConnection) => {
// Assert that service has requested correct url with expected method
expect(connection.request.method).toBe(RequestMethod.Get);
expect(connection.request.url).toBe('http://jsonplaceholder.typicode.com/posts');
// Send mock response
connection.mockRespond(new Response(new ResponseOptions({
body: mockResponse
})));
});
postsService.get()
.subscribe((posts) => {
expect(posts).toBe(mockResponse);
});
})));
});
