Karma 单元测试 EventEmitter 发射和订阅失败,无法读取未定义的属性“订阅”
Posted
技术标签:
【中文标题】Karma 单元测试 EventEmitter 发射和订阅失败,无法读取未定义的属性“订阅”【英文标题】:Karma unit test EventEmitter emit and subscribe failed, Cannot read property 'subscribe' of undefined 【发布时间】:2020-08-10 12:15:49 【问题描述】:我是 Angular/Node UT 的新手,目前,我添加了 karma 和 jasmine 来运行单元测试,我的应用程序基于 Angular7 + Node 8,遵循Angular test docs,大多数测试用例运行成功,但有些情况像@Input
@Output
(EventEmitter
) 数据测试失败。
请看我的代码并配置如下:
package.json
:
"jasmine-core": "~2.99.1",
"jasmine-spec-reporter": "~4.2.1",
"karma": "~3.0.0",
"karma-chrome-launcher": "~2.2.0",
"karma-coverage-istanbul-reporter": "~2.0.1",
"karma-jasmine": "~1.1.2",
"karma-jasmine-html-reporter": "^0.2.2"
a.component.ts
:
userDetailInit()
this.lookupService.genericServiceCall1(this.componentIds.componentUserDetail);
this.lookupService.compomentJsonEmit.subscribe(async o =>
// logic
, error =>
this.error("System Error");
);
lookupService
:
genericServiceCall1(iD)
let param =
'id': iD
;
this.compomentJsonEmit = new EventEmitter<Object>();
// getData() is a http request and will return data
this.commonService.getData('Get', param).subscribe(o =>
this.compomentJsonEmit.emit(o);
);
在单元测试文件agent-details.component.spec.ts
:
describe('UserDetailsComponent', () =>
let spy =
compJSONSpy: jasmine.createSpyObj('lookupService', ['genericServiceCall1']),
beforeEach(async(() =>
TestBed.configureTestingModule(
declarations: [ UserDetailsComponent ],
imports: [FormlyModule.forRoot(), HttpClientTestingModule],
providers: [
provide: CommonService, useValue: spy.comSpy ,
provide: LookupService, useValue: spy.compJSONSpy
],
schemas: [NO_ERRORS_SCHEMA ]
).compileComponents();
fixture = TestBed.createComponent(UserDetailsComponent);
component = fixture.componentInstance;
httpClient = TestBed.get(HttpClient);
httpTestingController = TestBed.get(HttpTestingController);
));
it('#timeChange(val) should set selectTimeZone to val', () =>
compJSONSpyReturn = spy.compJSONSpy.genericServiceCall1.and.returnValue(of(spyReturnJson.UserDetailCompJson));
component.componentIds =
componentUserDetail: 1007
;
// error occurred when run component.timeChange(12);
component.timeChange(12);
expect(compJSONSpyReturn.calls.any()).toBeDefined();
expect(component.selectTimeZone).toEqual(12);
);
);
因果报应报告:
TypeError: Cannot read property 'subscribe' of undefined
at userDetailsComponent.subscribe [as userDetailInit] (http://localhost:9876/_karma_webpack_/webpack:/src/app/admin/user-details/user-details.component.ts:77:46)
at userDetailsComponent.userDetailInit [as timeChange] (http://localhost:9876/_karma_webpack_/webpack:/src/app/admin/user-details/user-details.component.ts:109:14)
at UserContext.<anonymous> (http://localhost:9876/_karma_webpack_/webpack:/src/app/admin/user-details/user-details.component.spec.ts:66:15)
userListComponent #ngOninit() should be run
【问题讨论】:
【参考方案1】:this.lookupService.compomentJsonEmit
是undefined
。
试试:
const compomentJsonEmitSubject = new BehaviorSubject('hello'); // you can mock it how you like instead of 'hello'
describe('UserDetailsComponent', () =>
let spy =
compJSONSpy: jasmine.createSpyObj('lookupService', ['genericServiceCall1']),
spy.compJSONspy.compomentJsonEmit = componentJsonEmitSubject;
beforeEach(async(() =>
....
然后在你的测试中,如果你想要一个新的值componentJsonEmit
,你可以做componentJsonEmitSubject.next('goodbye');
【讨论】:
感谢 AliF50!根本原因如你所说。以上是关于Karma 单元测试 EventEmitter 发射和订阅失败,无法读取未定义的属性“订阅”的主要内容,如果未能解决你的问题,请参考以下文章
基于karma和jasmine的Angularjs 单元测试
使用 karma 和 jamis 进行 Angular 单元测试
茉莉花匹配器功能未在 angularjs/karma 单元测试中加载