如何对 Angular2 中的复选框进行单元测试

Question

I have a sample code for checkbox written with Angular2.

<div class="col-sm-7 align-left" *ngIf="Some-Condtion">
    <input type="checkbox" id="mob_Q1" value="Q1" />
    <label for="mob_Q1">Express</label>
</div>

I want to unit test the above checkbox. Like I want to recognize the checkbox and test whether it is check-able. How do I unit test this with Karma Jasmine?

Answer 1

Component, eg CheckboxComponent, contains input element. Unit test should looks like:

import {ComponentFixture, TestBed} from '@angular/core/testing';
import {By} from '@angular/platform-browser';
import {CheckboxComponent} from './checkbox.component';

describe('Checkbox test.', () => {

let comp: CheckboxComponent;
let fixture: ComponentFixture<CheckboxComponent>;
let input: Element;

beforeEach(() => {
    TestBed.configureTestingModule(
        {
            declarations: [CheckboxComponent],
        },
    );

    fixture = TestBed.createComponent(CheckboxComponent);
    comp = fixture.componentInstance;
    input = fixture.debugElement.query(By.css('#mob_Q1')).nativeElement;
});

it('should click change value', () => {
    expect(input.checked).toBeFalsy(); // default state

    input.click();
    fixture.detectChanges();

    expect(input.checked).toBeTruthy(); // state after click
});
});

Answer 2

IS there a need to write fixture.detectChanges() ?

I went through the same test without this and it ends with success. Button 1 is 'checked' by default

  const button1 = debugElement.nativeElement.querySelector(selectorBtn1);
  const button2 = debugElement.nativeElement.querySelector(selectorBtn2);
  ...
  expect(button1.checked).toBeTruthy();
  expect(button2.checked).toBeFalsy();

  button2.click();

  expect(button1.checked).toBeFalsy();
  expect(button2.checked).toBeTruthy();
  ...

Answer 3

ngModel directive is async one and requires to use asynchronous capabilities of Angular unit testing. Adding async and whenStable functions.

it('checkbox is checked if value is true', async(() => {
  component.model = true;
  fixture.detectChanges();

  fixture.whenStable().then(() => {
    const inEl = fixture.debugElement.query(By.css('#mob_Q1'));
    expect(inEl.nativeElement.checked).toBe(true);
  });
}));

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