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MockBackend

class deprecated

A mock backend for testing the Http service.

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Deprecated: see https://angular.io/guide/http

class MockBackend implements ConnectionBackend {
  connections: any
  connectionsArray: MockConnection[]
  pendingConnections: any
  verifyNoPendingRequests()
  resolveAllConnections()
  createConnection(req: Request): MockConnection
}

Description

This class can be injected in tests, and should be used to override providers to other backends, such as XHRBackend.

Properties

Property Description
connections: any EventEmitter

of MockConnection instances that have been created by this backend. Can be subscribed to in order to respond to connections.

This property only exists in the mock implementation, not in real Backends.

connectionsArray: MockConnection[]

An array representation of connections. This array will be updated with each connection that is created by this backend.

This property only exists in the mock implementation, not in real Backends.

pendingConnections: any EventEmitter

of MockConnection instances that haven't yet been resolved (i.e. with a readyState less than 4). Used internally to verify that no connections are pending via the verifyNoPendingRequests method.

This property only exists in the mock implementation, not in real Backends.

Methods

Checks all connections, and raises an exception if any connection has not received a response.

verifyNoPendingRequests()

Parameters

There are no parameters.

This method only exists in the mock implementation, not in real Backends.

Can be used in conjunction with verifyNoPendingRequests to resolve any not-yet-resolve connections, if it's expected that there are connections that have not yet received a response.

resolveAllConnections()

Parameters

There are no parameters.

This method only exists in the mock implementation, not in real Backends.

Creates a new MockConnection. This is equivalent to calling new MockConnection(), except that it also will emit the new Connection to the connections emitter of this MockBackend instance. This method will usually only be used by tests against the framework itself, not by end-users.

createConnection(req: Request): MockConnection

Parameters
req Request
Returns

MockConnection

Usage notes

Example

import {Injectable, Injector} from '@angular/core';
import {async, fakeAsync, tick} from '@angular/core/testing';
import {BaseRequestOptions, ConnectionBackend, Http, RequestOptions} from '@angular/http';
import {Response, ResponseOptions} from '@angular/http';
import {MockBackend, MockConnection} from '@angular/http/testing';

const HERO_ONE = 'HeroNrOne';
const HERO_TWO = 'WillBeAlwaysTheSecond';

@Injectable()
class HeroService {
  constructor(private http: Http) {}

  getHeroes(): Promise<String[]> {
    return this.http.get('myservices.de/api/heroes')
        .toPromise()
        .then(response => response.json().data)
        .catch(e => this.handleError(e));
  }

  private handleError(error: any): Promise<any> {
    console.error('An error occurred', error);
    return Promise.reject(error.message || error);
  }
}

describe('MockBackend HeroService Example', () => {
  beforeEach(() => {
    this.injector = Injector.create([
      {provide: ConnectionBackend, useClass: MockBackend},
      {provide: RequestOptions, useClass: BaseRequestOptions},
      Http,
      HeroService,
    ]);
    this.heroService = this.injector.get(HeroService);
    this.backend = this.injector.get(ConnectionBackend) as MockBackend;
    this.backend.connections.subscribe((connection: any) => this.lastConnection = connection);
  });

  it('getHeroes() should query current service url', () => {
    this.heroService.getHeroes();
    expect(this.lastConnection).toBeDefined('no http service connection at all?');
    expect(this.lastConnection.request.url).toMatch(/api\/heroes$/, 'url invalid');
  });

  it('getHeroes() should return some heroes', fakeAsync(() => {
       let result: String[];
       this.heroService.getHeroes().then((heroes: String[]) => result = heroes);
       this.lastConnection.mockRespond(new Response(new ResponseOptions({
         body: JSON.stringify({data: [HERO_ONE, HERO_TWO]}),
       })));
       tick();
       expect(result.length).toEqual(2, 'should contain given amount of heroes');
       expect(result[0]).toEqual(HERO_ONE, ' HERO_ONE should be the first hero');
       expect(result[1]).toEqual(HERO_TWO, ' HERO_TWO should be the second hero');
     }));

  it('getHeroes() while server is down', fakeAsync(() => {
       let result: String[];
       let catchedError: any;
       this.heroService.getHeroes()
           .then((heroes: String[]) => result = heroes)
           .catch((error: any) => catchedError = error);
       this.lastConnection.mockError(new Response(new ResponseOptions({
         status: 404,
         statusText: 'URL not Found',
       })));
       tick();
       expect(result).toBeUndefined();
       expect(catchedError).toBeDefined();
     }));
});

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Licensed under the Creative Commons Attribution License 4.0.
https://v7.angular.io/api/http/testing/MockBackend