DYP/src/app/contact-list/contact-list.page.spec.ts

import { ComponentFixture, TestBed } from '@angular/core/testing';
import { ContactListPage } from './contact-list.page';

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

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

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

  it('#clicked() should toggle #isOn', () => {
    const comp = new ContactListPage();
    expect(comp.isOn).withContext('off at first').toBe(false);
    comp.clicked();
    expect(comp.isOn).withContext('on after click').toBe(true);
    comp.clicked();
    expect(comp.isOn).withContext('off after second click').toBe(false);
  });
});