Forward Advance Learning

Testing Components

In order to unit test an Angular 2 component, we create an instance of that component, then check to see:

  • If it builds
  • if it contains what we expected it to contain

Assume we have a simple component like this:

import {Component} from '@angular/core';
selector: 'toaster',
template: `
export class ToasterComponent {

A simple test for this would simply build an instance, and check it doesn't die:

import { ComponentFixture, TestBed } from '@angular/core/testing';
import { ToasterComponent } from './toaster.component';
describe('ToasterComponent', () => {
let component: ToasterComponent;
let fixture: ComponentFixture<ToasterComponent>;
beforeEach(() => {
declarations: [ToasterComponent]
component = TestBed.createComponent(ToasterComponent).componentInstance;
it ('should work', () => {
expect(component instanceof ToasterComponent).toBe(true, 'should create ToasterComponent');

Checking the inside of a component

The above test only checks that the component builds. We may wish to check the html that actually gets generated

import { ComponentFixture, TestBed } from '@angular/core/testing';
import { By } from '@angular/platform-browser';
import { DebugElement } from '@angular/core';
import { CatNameComponent } from './cat_name.component';
describe('CatNameComponent', () => {
let component: CatNameComponent;
let fixture: ComponentFixture<CatNameComponent>;
let inputEl: DebugElement;
beforeEach(() => {
declarations: [CatNameComponent]
fixture = TestBed.createComponent(CatNameComponent);
component = fixture.componentInstance;
inputEl = fixture.debugElement.query(By.css('input')); // find cat search element
// Check it works
it ('should work', () => {
expect(component instanceof CatNameComponent).toBe(true, 'should create CatNameComponent');
// Check it has a cat name attribute
it ('should have a catName', () => {
// Check it has an input element
it ('should have a input element', () => {
expect(defined inputEl).toBe(true);

For more on this, see the guide here:!#simple-component-test

Attack the Dungeon Exercise

Use the github repository as a guide to create a component specs for your dungeon components.

You'll need a file called spec.ts. You can create this, or get it from the exercise startpoint. In it, you will require each of your component specs.

Create a spec.html to be your jasmine test harness, similar to the ones you have made before. You'll find one of these in your exerrcise startpoint.

Now create a new entry in webpack.config.js that builds the spec.ts file. You'll find this already present in the exercise starter.


You'll find code in the package.json to start a live reload server for your specs. Have a go at starting one of these now.