Jasmine and Karma

Created: Unit testing JS Apps using Jasmine and Karma

Updated: 03 September 2023

Jasmine

What and Why

What

Javascript testing framework
- Can be used with different languages and frameworks
  - Javascript, Node
  - Typescript, Angular
  - Ruby
  - Python
    
    Why
Fast
Independent
Runs via Node or in Browser
Behaviour Driven Development
- Attempts to describe tests in a human readable format

Setting up a test environment

For JS

<!-- Order of tags is important -->
<link rel="stylesheet" href="jasmine.css" />
<script src="jasmine.js"></script>
<script src="jasmine-html.js"></script>
<script src="boot.js"></script>

<!-- Sctipts to be tested -->
<script src="main.js"></script>

<!-- Test Script -->
<script src="test.js"></script>

For Node

Add Jasmine as a dev dependency

npm install --save-dev jasmine

Add test command to package.json

"scripts": { "test": "jasmine" }

Run the test command

npm test

Writing a test suite and spec

We want to test the following helloWorld function.

main.js

function helloWorld() {
  return 'Hello world!'
}

This function, when called should return 'Hello World'

test.js

describe('suiteName', () => {
  it('specName', () => {
    expect(helloWorld()).matcher('Hello world!')
  })
})

4 functions

Define the Test Suite
```
describe(string, function)
```
Define a Test Spec
```
it(string, function)
```
Define the Actual Value
```
expect(actual)
```
Define the Comparison
```
matcher(expected)
```

Setup and Teardown

let expected = 'Hello World!'

Initialize variable that are needed for testing

beforeAll(function)

Called before all tests in a Suite are run

afterAll(function)

Called after all tests in a Suite are run

beforeEach(function)

Called before each test Spec is run

afterEach

Called after each test Spec is run

Matchers

The means of comparing the actual and expected values
Return a boolean indicating if a test passed or failed

Jasmine has some pre-built Matchers

expect(array).toContain(member)
expect(fn).toThrow(string)
expect(fn).toThrowError(string)
expect(instance).toBe(instance)
expect(mixed).toBeDefined()
expect(mixed).toBeFalsy()
expect(mixed).toBeNull()
expect(mixed).toBeTruthy()
expect(mixed).toBeUndefined()
expect(mixed).toEqual(mixed)
expect(mixed).toMatch(pattern)
expect(number).toBeCloseTo(number, decimalPlaces)
expect(number).toBeGreaterThan(number)
expect(number).toBeLessThan(number)
expect(number).toBeNaN()
expect(spy).toHaveBeenCalled()
expect(spy).toHaveBeenCalledTimes(number)
expect(spy).toHaveBeenCalledWith(...arguments)

Custom matchers can also be defined

Running tests
For JS we have 2 options
Open index.html in a browser
Run npm test

Jasmine Demo

The following 3 files

index.html

<!DOCTYPE html>
<html>
  <head>
    <title>Jasmine Running</title>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link
      rel="stylesheet"
      href="https://cdnjs.cloudflare.com/ajax/libs/jasmine/2.4.1/jasmine.css"
    />
  </head>
  <body>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jasmine/2.4.1/jasmine.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jasmine/2.4.1/jasmine-html.js"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jasmine/2.4.1/boot.js"></script>
    <script src="main.js"></script>
    <script src="test.js"></script>
  </body>
</html>

main.js

function helloWorld() {
  return 'Hello world!'
}

function byeWorld() {
  return 'Bye world!'
}

function bigNumber(num) {
  return num + 1
}

test.js

describe('Test Suite', () => {
  let hello = ''
  let bye = 'Bye World :('
  let num = 0

  beforeAll(() => {
    num = 5
  })

  beforeEach(() => {
    hello = 'Hello world!'
  })

  afterEach(() => {
    hello = ''
    console.log('Test Completed')
  })

  it('Says hello', () => {
    expect(helloWorld()).toEqual(hello)
  })

  it('Says bye', () => {
    expect(byeWorld()).toEqual(bye)
  })

  it('Returns a bigger number', () => {
    expect(bigNumber(num)).toBeGreaterThan(num)
  })
})

Karma

What and Why

What

Test Runner for Jasmine in Angular
Automated running of tests
Does not require us to modify our code
Can test on multiple browser instances at once

Testing Angular Components

-ng generate component <component> will output:
- component.html
- component.css
- component.ts
- component.spec.ts
Test against an instance of a component
Using the Angular Test Bed

Angular Test Bed

Test behaviour that depends on Angular framework
Test Change and Property Binding
Import the TestBed, ComponentFixture and Component to be tested

import { TestBed, async } from '@angular/core/testing'
import { AppComponent } from './app.component'

Configure the Test Bed’s Testing Module with the necerssary components and imports in the beforeEach

Reinstantiate the component before each test

describe('AppComponent', () => {
beforeEach(async(() => {
  TestBed.configureTestingModule({
    declarations: [
      AppComponent
    ],
  }).compileComponents();
}));
...
});

Create a fixture and Component Instance

wrapper for a Component and Template

const fixture = TestBed.createComponent(AppComponent)
const app = fixture.debugElement.componentInstance

If a component has injected dependencies we can get these instances by:
```
const service = TestBed.get(ServiceName)
```

Looking at the App Component

app.component.html

<div style="text-align:center">
  <h1>Welcome to {{ title }}!</h1>
</div>
<h2>Here are some links to help you start:</h2>
<ul>
  <li>
    <h2><a target="_blank" rel="noopener" href="...">Tour of Heroes</a></h2>
  </li>
  <li>
    <h2><a target="_blank" rel="noopener" href="...">CLI Documentation</a></h2>
  </li>
  <li>
    <h2><a target="_blank" rel="noopener" href="...">Angular blog</a></h2>
  </li>
</ul>

app.component.ts

import { Component } from '@angular/core'

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
})
export class AppComponent {
  title = 'app'
}

app.component.spec.ts

import { TestBed, async } from '@angular/core/testing'
import { AppComponent } from './app.component'
describe('AppComponent', () => {
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [AppComponent],
    }).compileComponents()
  }))
  it('should create the app', async(() => {
    const fixture = TestBed.createComponent(AppComponent)
    const app = fixture.debugElement.componentInstance
    expect(app).toBeTruthy()
  }))
  it(`should have as title 'app'`, async(() => {
    const fixture = TestBed.createComponent(AppComponent)
    const app = fixture.debugElement.componentInstance
    expect(app.title).toEqual('app')
  }))
  it('should render title in a h1 tag', async(() => {
    const fixture = TestBed.createComponent(AppComponent)
    fixture.detectChanges()
    const compiled = fixture.debugElement.nativeElement
    expect(compiled.querySelector('h1').textContent).toContain(
      'Welcome to app!'
    )
  }))
})

Running tests with the AngularCLI

ng test
Other Angular features can also be tested
- Services
- Components
- Classes
- Forms
- Routing
- Dependency Injection
- etc.

Karma Demo

Conclusion

Jasmine is a relatively simple testing tool
- Easy to implement on a variety of projects
Karma Automates testing
- Test on multiple places simultaneously
- Well incorporated into Angular