Testing OnPush components in Angular

Question

I am having trouble testing a component with OnPush change detection strategy.

The test goes like this

it('should show edit button for featured only for owners', () => {
    let selector = '.edit-button';

    component.isOwner = false;
    fixture.detectChanges();

    expect(fixture.debugElement.query(By.css(selector))).toBeFalsy();

    component.isOwner = true;
    fixture.detectChanges();

    expect(fixture.debugElement.query(By.css(selector))).toBeTruthy();
});

If I use Default strategy it works as expected, but with OnPush the change to isOwner is not rerendered by the call to detectChanges. Am I missing something?

Answer 1

If you check out this great @Günter's answer angular 2 change detection and ChangeDetectionStrategy.OnPush then you can work around it by using event handler like:

const fixture = TestBed.overrideComponent(TestComponent, {set: {host: { "(click)": "dummy" }}}).createComponent(TestComponent);
// write your test
fixture.debugElement.triggerEventHandler('click', null);
fixture.detectChanges();

Here's Plunker Example