How to unit test the checkbox in Angular2 - unit-testing

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, e.g. 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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