单元测试出错：

Error: : handleError() method does not exist
Usage: spyOn(, )
at
at UserContext.apply (http://localhost:9876/karma_webpack/src/global-message/http-interceptors/http-error.interceptor.spec.ts:121:9)
at ZoneDelegate.invoke (http://localhost:9876/karma_webpack/C:/Code/SPA/spartacus/node_modules/zone.js/dist/zone.js:386:30)
at ProxyZoneSpec.onInvoke (http://localhost:9876/karma_webpack/C:/Code/SPA/spartacus/node_modules/zone.js/dist/zone-testing.js:292:43)
at ZoneDelegate.invoke (http://localhost:9876/karma_webpack/C:/Code/SPA/spartacus/node_modules/zone.js/dist/zone.js:385:36)
at Zone.run (http://localhost:9876/karma_webpack/C:/Code/SPA/spartacus/node_modules/zone.js/dist/zone.js:143:47)
at runInTestZone (http://localhost:9876/karma_webpack/C:/Code/SPA/spartacus/node_modules/zone.js/dist/zone-testing.js:545:38)
at UserContext. (http://localhost:9876/karma_webpack/C:/Code/SPA/spartacus/node_modules/zone.js/dist/zone-testing.js:560:24)

原因出在下图高亮的这行代码上：

handlerClass的类型是一个function，而不是具体的对象实例。因此，handler.handleError为undefined：

实际上，一个function可用的属性有且仅有下列几种：

使用下列代码后错误消失：

const handler = TestBed.inject(handlerClass) as HttpErrorHandler;

更多Jerry的原创文章，尽在：“汪子熙”: