What Is Unit Testing In Angular

What Is Unit Testing in Angular?

Angular is a platform and application design framework for building sophisticated, high-performing single-page apps.

You can test a particular Angular code unit in isolation with the aid of Angular unit tests. Angular unit tests isolate specific areas of your code to expose issues such as flawed reasoning, coding mistakes, or broken functionalities.

Achieving unit testing can be challenging for intricate applications with inadequate concern separation. But with Angular, you can design code in a way that makes it simple to test each feature of your application separately. It should be simple to add unit tests to your applications if you prepare for unit testing ahead of time and adhere to Angular code best practices.

Also, Read An Introduction To API Testing

Why Is Unit Testing of Angular Apps Important?

You may check your application for coding bugs and unusual user behavior with Angular unit tests. It can be time-consuming and ineffective to test every potential behavior, but creating tests for each coupling block in your application will help you find issues with each one.

The creation of a test for each block is among the simplest methods for determining that block's strength. Rather than waiting for a bug to show up in production, you should take this action. Unit tests can be written for blocks (components, services, etc.) to help find and repair errors early in the development cycle.

Angular Component Testing Fundamentals

Testing angular components entails evaluating the functionality and calibre of application components. You can manually test Angular components by launching the application and observing whether the components function as anticipated. However, for large, complicated online applications, manual testing is both time-consuming and impractical. Finding a more effective method to test Angular components will probably be necessary.

Jasmine and Karma are included in Angular applications that use the Angular CLI to streamline and automate the testing procedure. You can create unit tests using the behavior-based testing framework Jasmine. After that, you can test Karma to see if each component of the application is operating as intended. If there are no bugs in the code, the unit tests pass; otherwise, they fail.

The naming convention name.component.spec.ts should be followed by the test files. It is recommended to keep them among the other files related to the same component. Unit tests for the core AppComponent are contained in the app.component.spec.ts file, which you may have seen if you built your Angular application with the Angular CLI. All of the unit tests contained in the *.spec.ts files are executed when you run tests using the Angular CLI.

To run tests using the Angular CLI, type the ng test command into the terminal. It will cause Karma to launch the built-in browser and launch the tests you created with Jasmine, displaying the results.

Also, Read An Introduction To Performance Testing

Here are a few of Jasmine's fundamental features:

-describe(string, function) – accepts a function with one or more specs as well as a title. Another name for it is a test suite.
-The function it(string, function) accepts a title and a function with one or more expectations. Another name for it is specifications.
-expect(actual) – accepts an actual as a parameter. Expect functions are typically used in conjunction with matcher functions. Together, they yield boolean values that indicate whether a specification is passed or failed.
-The matcher accepts a value that stands for the anticipated value. Expect functions are linked to matcher functions. ToBeTruthy(), toContain(), and toEqual() are a few matches.

For example:

An application component that ought to operate in the testing environment is declared in the beforeEach block. An example of a beforeEach block can be found here. Keep in mind that if you are using webpack, you might not require the compileComponents() function.

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

Verifying that an instance of the application component is correctly created is the first step in a unit test. Take a look at the code below; an instance of your component is generated by the property fixture.debugElement.componentInstance. The code uses the assertion toBeTruthy to determine whether the component was built.

it('component should be created', async(() => {
 const fixture = TestBed.createComponent(MyComponent);
 const app = fixture.debugElement.componentInstance;
 expect(app).toBeTruthy();
}));

Let's now create another code block that indicates whether we may access the component's properties. The test that follows determines whether the title displayed in the browser upon component rendering is accurate. Naturally, you would need to replace the current title defined in the component with my-title.

it(`component should have title 'my-title'`, async(() => {
 const fixture = TestBed.createComponent(MyComponent);
 const app = fixture.debugElement.componentInstance;
 expect(app.title).toEqual('my-title');
}));

Lastly, we can examine the DOM elements that the component has produced. Let's examine the <h1> HTML tag that the component produced. We are going to emulate running in a browser context by using the detectChanges() function. We may access a real on-page DOM element using the fixture.debugElement.nativeElement attribute.

it('component should render 'Welcome to My App' in h1 tag', async(() => {
 const fixture = TestBed.createComponent(MyComponent);
 fixture.detectChanges();
 const compiled = fixture.debugElement.nativeElement;
 expect(compiled.querySelector('h1').textContent).toContain('Welcome to My App!');
}));

This is a short video that shows you how to load an Angular application component, test it in a testing environment, and check various elements of the component in a browser-simulation environment using a specs.ts file.