Jasmine 试图读取不存在的属性

Question

I have an extremely simple component:

import { Component } from '@angular/core';

@Component({
    selector: 'loading',
    templateUrl: './loading.component.html',
    styleUrls: ['./loading.component.scss']
})
export class LoadingComponent {
}

which just displays a static loading logo. No interactivity at all. I wrote a test just to test its instantiation:

import { async, ComponentFixture, TestBed } from '@angular/core/testing';

import { LoadingComponent } from './loading.component';

describe('LoadingComponent', () => {
    let component: LoadingComponent;
    let fixture: ComponentFixture<LoadingComponent>;

    beforeEach(async(() => {
        TestBed.configureTestingModule({
            declarations: [ LoadingComponent ]
        })
        .compileComponents();
    }));

    beforeEach(() => {
        fixture = TestBed.createComponent(LoadingComponent);
        component = fixture.componentInstance;
        fixture.detectChanges();
    });

    it('should exist', () => {
        expect(component).toBeTruthy();
    });
});

In Firefox, this test throws an error: j is undefined , and in Chromium browsers I see Cannot read property 'startTime' of undefined . The template is simply:

Sample Text

for the sake of figuring out what's going on. So there's no mention of 'startTime' anywhere in those three files - what's going on??

Note

I do use startTime properties in other components, but I can't figure out how/why that would matter.

Edit

I've been able to get this error to disappear by just adding:

afterAll(() => {
    TestBed.resetTestingModule();
});

to every single test in the project. I'm leaving the question open because I have no idea:

1. Why this works/what the underlying problem was
2. If I'm swinging a heavier axe than I need to - would adding it to only one test suffice?

Answer 1

The error you are seeing is definitely not coming from component and spec file you have posted. The error you are seeing is most likely coming from a component that does an async operation and the error occurs after the spec that instantiated it has already finished.

First off put an f in frontof the describes of this spec file.

fdescribe('LoadingComponent', () => {

This will cause the spec runner to only run this file. You will see that it passes fine.

Next you want to remove the f and the search your project for startTime, try running specs for components that use the property startTime one at a time.

If you can't locate it then put an x in front of the describes of them one at a time, eventually you will find which one is causing the error as it wont happen when you have an x on the spec that causes the error.

Any specs that do async function should use the async function so that it waits for all async activity to finish before moving on to the next spec.