Angular 4 - karma不接受函数作为html隐藏属性，它说“XY不是函数”

Question

我正在尝试测试路由。 我有一个函数来检查我是否已登录，这是在Login / Logout按钮隐藏属性中作为语句给出的。 HTML：     登录

<a [hidden]="setLoggedOut()" routerLink="/login"
(click)="clearSessionStorage()">Logout</a>

登录/ LogoutChecker

setLoggedOut = () => {
    let loggedOut = true;
    const currentUser = sessionStorage.Status;
    if (currentUser === 'ok') {
        loggedOut = false;
    }
    return loggedOut;
 }

在测试期间，我收到以下错误消息： TypeError：compo.setLOggedOut不是函数

这是测试组件：

import { Component } from '@angular/core';
import { Location } from '@angular/common';
import { CanActivate, Router } from '@angular/router';
import { RouterTestingModule } from '@angular/router/testing';
import { async, inject, TestBed } from '@angular/core/testing';
import { FormsModule } from '@angular/forms';
import { Http, ConnectionBackend, RequestOptions } from '@angular/http';

import { HomeComponent } from './home/home.component';
import { LoginComponent } from './login/login.component';
import { RoutingService } from './routing.service';
import { AppComponent } from './app.component';

class requestoptions {
    public requestoption: RequestOptions
}

@Component ({
    templateUrl: './app.component.html'
})
class RoutingComponent {  }

describe('component: RoutingComponent', () => {
    let location, routing, compo;

    beforeEach(() => {
        TestBed.configureTestingModule({
            imports: [
                FormsModule,
                RouterTestingModule.withRoutes([
                    { path: 'login', component: LoginComponent },
                    { path: '', component: HomeComponent, canActivate: 
[RoutingService] }
                ])
            ],
            declarations: [
                AppComponent,
                RoutingComponent,
                HomeComponent,
                LoginComponent
            ], 
            providers: [
                 RoutingService,
                 {provide: Http, useClass: requestoptions},
                 ConnectionBackend
            ]
        });
    });

    beforeEach(inject([Router, Location], (_router: Router, _location: 
Location) => {
        location = _location;
        routing = _router;
    }));

    it('should go home', async(() => {
        const fixture = TestBed.createComponent(RoutingComponent);
        fixture.detectChanges();
        routing.navigate(['']).then(() => {
            expect(location.path()).toBe('/');
            console.log('after expect');
        });
    }));


    it('should go to the login page', async(() => {
        const fixture = TestBed.createComponent(RoutingComponent);
        fixture.detectChanges();
        routing.navigate(['login']).then(() => {
            expect(location.path()).toBe('/login');
            console.log('after expect');
        });
    }));
});