在 angular 服务中初始化时，array.some 在运行 ng-test 期间不是函数

问题描述

我通过从缓存中获取 allUsers 来初始化它，然后使用 specialUserExists (Array.prototype.some() for reference) 将布尔值从 allUsers 分配给 allUsers.some()。

service.ts

@Injectable({
  providedIn: 'root'
})
export class SomeService {

  private allUsers: User[] = this.storageService.getItem('SOME_KEY');
  private specialUserExists = this.allUsers.some(user => user.inSpecialGroup);

  constructor(
    private filterService: FilterService,private storageService: StorageService,) { }
}

在 service.specs.ts 中，我编写了如下测试用例 service.specs.ts：

describe('SomeService',() => {
  let service: SomeService;

  beforeEach(() => {
    service = new SomeService(
      mockFilterService.object(),mockStorageService.object(),);
  });

  it('should be created',() => {
    expect(service).toBeTruthy();
  });
}

在运行 ng-test 时出现以下错误：

<SomeService> should be created
TypeError: this.allUsers.some is not a function
    at <Jasmine>
    at new BreakdownService (http://localhost:9876/_karma_webpack_/src/app/_shared/services/some.service.ts:33:48)
    at UserContext.<anonymous> (http://localhost:9876/_karma_webpack_/src/app/_shared/services/some.service.spec.ts:19:15)
    at ZoneDelegate.invoke (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-evergreen.js:359:1)
    at ProxyZonespec.onInvoke (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-testing.js:308:1)
    at ZoneDelegate.invoke (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-evergreen.js:358:1)
    at Zone.run (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-evergreen.js:124:1)
    at runInTestZone (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-testing.js:561:1)
    at UserContext.<anonymous> (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-testing.js:576:1)
    at <Jasmine>
    at ZoneDelegate.invokeTask (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-evergreen.js:391:1)
    at Zone.runTask (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-evergreen.js:168:1)
Expected undefined to be truthy.
error properties: Object({ originalStack: 'Error: Expected undefined to be truthy.
    at new ZoneAwareError (http://localhost:9876/_karma_webpack_/node_modules/zone.js/dist/zone-error.js:100:1)
    at stack (http://localhost:9876/base/node_modules/jasmine-core/lib/jasmine-core/jasmine.js?)
    at buildExpectationResult (http://localhost:9876/base/node_modules/jasmine-core/lib/jasmine-core/jasmine.js?)
    at Spec.expectationResultFactory (http://localhost:9876/base/node_modules/jasmine-core/lib/jasmine-core/jasmine.js?)
    at Spec.addExpectationResult (http://localhost:9876/base/node_modules/jasmine-core/lib/jasmine-core/jasmine.js?)
    at Expector.addExpectationResult (http://localhost:9876/base/node_modules/jasmine-core/lib/jasmine-core/jasmine.js?)
    at Exp ...
Error: Expected undefined to be truthy.
    at <Jasmine>

代码按预期运行并正确给出输出。 我无法找出测试用例错误。

我该如何解决这个问题？

解决方法

您必须确保 mockStorageService 具有返回数组的 getItem 方法。

尝试这样的事情：

describe('SomeService',() => {
  let service: SomeService;

  beforeEach(() => {
    service = new SomeService(
      mockFilterService.object(),{
        getItem(key: string): {
          return []; // mock the array to be returned here.
        } 
      }
    );
  });

  it('should be created',() => {
    expect(service).toBeTruthy();
  });
}