为什么detectChanges()之后复选框选中的属性没有更改 [英] Why checkbox checked property doesn't change after detectChanges()

问题描述

我尝试通过更改模型来更改复选框选中的属性，但是它不起作用.我无法理解这种行为.

I try to change checkbox checked property by changing model but it doesn't work. I cannot understand this behavior.

模板:

<input type="checkbox" [(ngModel)]="model"/>

测试代码:

    it('should be checked after click on unchecked checkbox', () => {
        const checkbox: HTMLInputElement = fixture.nativeElement.querySelector('input');

        component.model = true;
        fixture.detectChanges();
        expect(checkbox.checked).toBeTruthy();
    });

完整代码: https://stackblitz.com/edit/angular-testing-checkbox?file=app/app.component.spec.ts

推荐答案

因为角度变化检测是异步的.您的expect()语句发生在更改检测完成之前.在测试中使用角度测试async()函数:

Because angular change detection is asynchronous. Your expect() statement happenned before change dectection is finished. Use angular testing async() function in your test :

   it('should be checked after click on unchecked checkbox', async( () => {
        const checkbox: HTMLInputElement = fixture.nativeElement.querySelector('input');    
        component.model = true;
        fixture.detectChanges();    
        fixture.whenStable().then(()=> {
          expect(checkbox.checked).toBeTruthy();
        })   
    }));

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