What Is Unit Testing In Angular
What Does Angular Unit Testing Entail?
A platform and application design framework called Angular is used to create complex, high-performing single-page applications.
Angular unit tests help you test a specific Angular code unit in isolation. Angular unit tests isolate particular sections of your code to reveal problems like faulty logic, erroneous coding, or malfunctioning features.
Completing unit testing for complex programmes with insufficient separation of concerns can be difficult. However, you may write code with Angular in a way that makes it easy to test your application’s features independently. If you follow Angular coding best practices and prepare for unit testing in advance, adding unit tests to your applications should be straightforward.
Also, Read An Introduction To API Testing
Why Is Angular App Unit Testing Important?
Angular unit tests can be used to test your application for anomalous user behaviour and coding errors. Testing every possible behaviour may be time-consuming and inefficient, but by developing tests for each coupling block in your application, you may identify problems with each one.
One of the simplest ways to figure out a block’s strength is to create a test for it. You should do this instead of waiting for a bug to manifest itself in production. For blocks (components, services, etc.), unit tests can be designed to aid in the early detection and correction of faults during the development cycle.
Principles of Angular Component Testing
Evaluating the functionality and quality of application components is necessary for testing angular components. Angular components can be manually tested by starting the application and seeing if the components perform as expected. However, manual testing is impracticable and time-consuming for large, complex web systems. Most likely, a more efficient way to test Angular components will need to be found.
Angular apps that use the Angular CLI to automate and streamline the testing process come with Jasmine and Karma. Using the behavior-based testing framework Jasmine, unit tests may be written. Following that, you may test Karma to make sure every part of the programme is working as it should. The unit tests succeed if there are no bugs in the code; they fail if there are.
The test files should use the name.component.spec.ts naming convention. It is advised to preserve them with the other files pertaining to the same part. If you used the Angular CLI to build your Angular application, you may have encountered the app.component.spec.ts file, which contains unit tests for the main AppComponent. When you run tests using the Angular CLI, every unit test in the *.spec.ts files is run.
Enter the ng test command into the console to begin testing with the Angular CLI. Karma will then start the integrated browser, open the tests you made using Jasmine, and show the outcomes.
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.
As an illustration:
The beforeEach block declares an application component that should function in the testing environment. This is an illustration of a beforeEach block. Remember that you may not need the compileComponents() function if you are using webpack.
beforeEach(async(() => {
TestBed.configureTestingModule({
declarations: [
MyComponent
],
}).compileComponents();
}));
A unit test starts by confirming that an instance of the application component is created correctly. Look at the code below; the property fixture creates an instance of your component.componentInstance.debugElement. To ascertain whether the component was constructed, the code makes use of the assertion toBeTruthy.
it(‘component should be created’, async(() => {
const fixture = TestBed.createComponent(MyComponent);
const app = fixture.debugElement.componentInstance;
expect(app).toBeTruthy();
}));
Now let’s write another code block to signal whether or not we can access the properties of the component. The test that follows checks the accuracy of the title that appears in the browser when a component renders. It goes without saying that you would have to use my-title in place of the existing title defined in the component.
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 little video demonstrates how to load an Angular application component, test it in a testing environment, and use a specs.ts file to examine different component aspects in a browser-simulation environment.
