order.component.spec.ts

// order.component.spec.ts
import { TestBed, ComponentFixture } from '@angular/core/testing';

import { OrderComponent } from './order.component';
import { DebugElement } from '@angular/core';

describe('OrderComponent', () => {
  let fixture: ComponentFixture<OrderComponent>;
  let component: OrderComponent;
  let debugElement: DebugElement;

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

    fixture = TestBed.createComponent(OrderComponent);
    component = fixture.componentInstance;
    debugElement = fixture.debugElement;
  });

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

  describe('order null', () => {
    it('should display empty template.', () => {
      // Setting order to null
      component.order = null;

      // Triggering change detection
      fixture.detectChanges();

      // Checking template
      expect(debugElement.nativeElement.textContent).toEqual('');
    });
  });

  describe('order not null', () => {
    it('should display order value formatted as number.', () => {
      // Setting order to null
      component.order = {date: '2000-01-01', product: 'product 1', value: 1000};

      // Triggering change detection
      fixture.detectChanges();

      // Checking template
      expect(debugElement.nativeElement.textContent).toEqual('1,000');
    });
  });
});