如何在 Angular 中模拟查询参数以进行服务测试？

Question

我正在尝试从 Angular 中的服务测试可观察的，这取决于 queryParam 的值。

在尝试模拟 queryParam 以便能够对 observable 执行测试时，我非常卡住。

我尝试了不同的方法，但我无法实现 queryParam 值。

这是服务：

import { Injectable } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { BehaviorSubject, Observable } from 'rxjs';

@Injectable({
  providedIn: 'root',
})
export class CarService {
  private readonly _car$: BehaviorSubject<boolean> = new BehaviorSubject<boolean>(this.carStatus);

  constructor(private route: ActivatedRoute) {}

  public get car$(): Observable<boolean> {
    return this._car$.asObservable();
  }

  private get carStatus(): boolean {
    const isHybrid = this.route.snapshot.queryParamMap.get('hybrid') === 'true';
    if (isHybrid) return true;
    return false;
  }
}

这些是测试文件的不同方法：

选项1

import { TestBed } from '@angular/core/testing';
import { ActivatedRouteSnapshot } from '@angular/router';
import { RouterTestingModule } from '@angular/router/testing';

import { CarService } from './carService.service';


describe('CarService', () => {
  let service: CarService;
  let route: ActivatedRouteSnapshot;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [RouterTestingModule],
      providers: [CarService],
    });
    route = new ActivatedRouteSnapshot();
  });

  describe('When there is a hybrid car', () => {
    it('should enable the electric mode', (done) => {
      route.queryParams = {
        hybrid: 'true',
      };
      service = TestBed.inject(CarService);

      service.car$.subscribe((value: boolean) => {
        expect(value).toBe(true);
        done();
      });
    });
  });

  describe('When the car is not hybrid', () => {
    it('should NOT enable the electric mode', (done) => {
      route.queryParams = {
        hybrid: 'false',
      };
      service = TestBed.inject(CarService);

      service.car$.subscribe((value: boolean) => {
        expect(value).toBe(false);
        done();
      });
    });
  });

选项 2

import { TestBed } from '@angular/core/testing';
import { ActivatedRouteSnapshot } from '@angular/router';
import { RouterTestingModule } from '@angular/router/testing';

import { CarService } from './carService.service';


describe('CarService', () => {
  let service: CarService;
  let route: ActivatedRouteSnapshot;

    beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [RouterTestingModule],
      providers: [
        CarService,
        {
          provide: ActivatedRouteSnapshot,
          useValue: {
            snapshot: {
              queryParams: {
               hybrid: ‘true’,
              },
            },
          },
        },
      ],
    });
    route = TestBed.inject(ActivatedRouteSnapshot);
    service = TestBed.inject(CarService);
  });

  describe('When there is a hybrid car', () => {
    it('should enable the electric mode', (done) => {

      service.car$.subscribe((value: boolean) => {
        expect(value).toBe(true);
        done();
      });
    });
  });

选项 3 使用 spyOn

 describe('When there is a hybrid car', () => {
    it('should enable the electric mode', (done) => {
       const route = new ActivatedRouteSnapshot();
       spyOn(route.queryParamMap, 'get').and.returnValue('true');

       service = TestBed.inject(CarService);

     service.car$.subscribe((value: boolean) => {
        expect(value).toBe(true);
        done();
      });
    });
  });

我还尝试在此处的文档中实现 ActivatedRouteStub（ https://angular.io/guide/testing-components-scenarios#routed-components ），但我得到的点与前面的选项相同。 服务中的 get carStatus() 永远无法读取 queryParam，因为它是空的。

如果有人可以帮助我，我将不胜感激。

Answer 1

试试这个（我们使用选项 1）：

import { TestBed } from '@angular/core/testing';

import { CarService } from './carService.service';


describe('CarService', () => {
  let service: CarService;
  let route: ActivatedRoute;
  let queryParamMapGet: jasmine.Spy;

  beforeEach(() => {
    // create a spy for the get method
    queryParamMapGet = jasmine.createSpy('queryParamMapGet');
    TestBed.configureTestingModule({
      providers: [CarService
        { 
          provide: ActivatedRoute, 
          useValue: { 
           snapshot: {
              queryParamMap: {
                        get: queryParamMapGet // assign it to the get spy
              } 
          } 
         } 
        }
      ],
    });
  });

  describe('When there is a hybrid car', () => {
    it('should enable the electric mode', (done) => {
      // return true for the get value
      queryParamMapGet.and.returnValue('true');

      service = TestBed.inject(CarService);

      service.car$.subscribe((value: boolean) => {
        expect(value).toBe(true);
        done();
      });
    });
  });

  describe('When the car is not hybrid', () => {
    it('should NOT enable the electric mode', (done) => {
      // return false for the get value
      queryParamMapGet.and.returnValue('true');

      service = TestBed.inject(CarService);

      service.car$.subscribe((value: boolean) => {
        expect(value).toBe(false);
        done();
      });
    });
  });