Jasmine单元测试中的MockService的UseValue导致测试失败

问题描述

我创建了一个运行Stack/Jasmine加载程序的StackBlitz ，因此您可以查看测试通过/失败.

I've created a StackBlitz with the karma/jasmine loader running so you can see the test pass/fail.

应用程序可以正常工作.

The application is working as it should.

我的测试应该可以并且可以通过，但是我在使用模拟服务而不是对createspyobject启用的适当服务时遇到了一个奇怪的错误.

My tests should be ok and will pass, however I'm getting a strange error with using a mockservice instead of the proper service to createspyobject on.

component.ts

  getReportFunc(): void {
    this.reportService.getReport(this.urn).subscribe(selectedReport => {
      this.model = selectedReport;
    });
  }

对服务的简单调用以获取"getReport".我将添加一个测试以检查该报告是否已被调用.但是由于这个问题而不能.

Simple call to a service to fetch "getReport". I will add a test to check that the report has been called. however cant because of this issue.

spec.ts

describe("SearchComponent", () => {
  let component: SearchComponent;
  let fixture: ComponentFixture<SearchComponent>;
  let mockReportService;

  beforeEach(async(() => {
      mockReportService = jasmine.createSpyObj(['getReport']);
    TestBed.configureTestingModule({
      declarations: [SearchComponent],
      providers: [
        //ReportService,
            { provide: ReportService, useValue: mockReportService },
...

问题在于仅使用ReportService的{ provide: ReportService, useValue: mockReportService }可以正常运行，但这意味着我无法运行我的测试之一.我想创建一个间谍对象mockReportService = jasmine.createSpyObj(['getReport']);.

The issue is with { provide: ReportService, useValue: mockReportService } using just ReportService will run fine but it means I cant run one of my tests. I want to create a spy object mockReportService = jasmine.createSpyObj(['getReport']);.

您将在 StackBlitz 是那个TypeError: Cannot read property 'subscribe' of undefined.

如果有人可以帮助我使它与模拟服务一起运行，以便我可以测试getReport订阅功能，我将不胜感激.

If somebody can help me getting this to run with a mockservice so I can test the getReport subscribe function I would be most grateful.

推荐答案

问题来自jasmine.createSpyObj的误用.您有2个选择:

The problem comes from a misuse of jasmine.createSpyObj You have 2 options :

1. 以正确的方式使用jasmine.createSpyObj:

// Note the first arg, you were missing it
mockReportService = jasmine.createSpyObj(ReportService, ['getReport']);


// Then, explain what to do with it :
beforeEach(() => {
  [...]
  // When called, make it return an Observable so that the call to subscribe() succeeds
  mockReportService.getReport.and.returnValue(of({}));
  fixture.detectChanges();
});

1. 不要使用间谍

当然，间谍很整洁，但是仅当您想在不同的单元测试期间更改返回的值时，它们才有用.如果您只需要始终返回一个值，那么无论哪个，您都可以选择像这样的硬编码对象:

Sure, spies are neat but they are useful only if you want to change the returned values during the different unit tests. If you just need to always return a value, no matter which, you can opt for a hardcoded object like this :

  const mockReportService = {
    getReport: () => of({})
  }

  providers: [
    { provide: ReportService, useValue: mockReportService },

这篇关于Jasmine单元测试中的MockService的UseValue导致测试失败的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！