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A Practical Approach To Angular Testing

A Practical Approach To Angular Testing

June 14, 2022
 by 
Kazuaki Matsuo

Testing is an integral part of the software development process. It allows developers to verify that their code works as expected and helps them catch errors before they cause problems in production. In this article, we'll look at how to test Angular applications. We'll start with unit testing, then move on to end-to-end testing. We'll also look at some of the best tools for Angular testing.

What is Angular testing, and why do you need it?

Angular testing is verifying that your Angular code behaves as expected. It's essential to test your code thoroughly because errors in production can be costly and difficult to fix. You can catch defects early on by writing tests before they cause problems.

There are several advantages of angular testing:

  • It helps you verify that your code works as expected.
  • It enables you to catch errors early on before they cause problems.
  • It makes it easier to make changes to your code.
  • It helps ensure that your code is reliable and stable.

Type of Testing in Angular

There are two main types of Angular testing: unit testing and end-to-end testing. Unit testing is verifying that individual units of code behave as expected. End-to-end testing is verifying that the entire application behaves as expected.

There are a variety of tools available for Angular testing. This article will look at some of the best options for both unit testing and end-to-end testing.

Unit Testing

Unit testing is a type of testing that verifies the functionality of individual units of code. A unit can be a component, service, pipe, directive, or anything else in an Angular application. Unit tests are written using a variety of frameworks and tools. Popular Angular unit testing options are Jasmine, Karma, and Jest.

To write a unit test, you first need to create a test case. A test case is simply a piece of code that exercises the unit you're testing and verifies that it behaves as expected. Once you've written your test case, you can run it using a unit testing framework. The framework will execute the code in your test case and report whether it passed or failed.

"Test-driven development" is one development approach. You first write the unit test and then write the code that makes the test pass as a guide. This approach has several benefits, including:

  • It forces you to think about what you want your code to do before writing it. This can help you catch errors early on.
  • It makes your code more modular and easier to change. Each unit is only responsible for a small part of the overall functionality.
  • It makes your code easier to test. Each unit is isolated from the others, so it's easy to test one unit without affecting the others.

End-to-End Testing

In addition to unit testing, you also need to do end-to-end testing. End-to-end testing is a type of testing that verifies the functionality of an entire application from start to finish. This includes everything from loading the page to submitting a form.

There are a few different tools you can use for end-to-end testing, but one of the best options for Angular is Protractor. Protractor is a tool that was designed explicitly for end-to-end testing of Angular applications. It's easy to use and has many features that make it well suited for this type of testing.

When you're doing end-to-end testing, it's essential to keep a few things in mind. First, you need to make sure that you're testing the application as a whole, not just individual pieces. This means testing all of the interactions between different parts of the application. Second, you need to test the application from a real user's perspective. This means using a real browser and interacting with the application the way a user would.

Tools for Angular Testing

There are several different tools you can use for Angular testing. Some popular options include:

  • Karma: Karma is a JavaScript test runner that lets you run your tests in a real browser. This is important because it allows you to test your code in the same environment that it will be executed in when your application is deployed.
  • Jasmine: Jasmine is a behavior-driven development framework for JavaScript. It provides a suite of tools for writing and running tests.
  • Protractor: Protractor is an end-to-end testing tool for Angular applications. It runs your tests in a real browser and simulates how a user would interact with your application.
  • Angular CLI: The Angular CLI (Command Line Interface) is a tool that you can use to scaffold, generate, and test Angular applications.

Choosing the right tool depends on your needs. The Angular CLI is a good option if you're just getting started with Angular testing. It's easy to use, and it comes with everything you need to get started. If you're looking for a more powerful tool, Karma or Protractor may be a better fit.

How to write a simple unit test in Angular

First, let's look at how to write a simple unit test in Angular. We'll use the example of a simple calculator.

The calculator has two functions: add and subtract. We'll write a unit test for the add function.

The test case will verify that the add function correctly adds two numbers. Here's the code for the test case:


import { Calculator } from './calculator.js';
describe('add', () => {
it('adds two numbers together correctly', (expected) => {
const calculator = new Calculator();
const result = calculator.add(1, 2);
expect(result).toEqual(3);
});
});

There are a few things to note about this code. First, we're using the expectfunction to verify that the add function returns the correct result. This is a standard assertion function that Jasmine provides. Second, we're using the new keyword to create an instance of the Calculator class.

This is necessary because our test case is in a different file than the calculator itself. Finally, we're passing in 1 and 2 as arguments to the add function. These are the numbers that we expect the add function to add together.

Now let's look at how to write an end-to-end test in Angular using Protractor. We'll use the same example of a simple calculator.

The test case will verify that the add function works correctly when used in a real browser. Here's the code for the test case:


import { by, element } from 'protractor';
describe('add', () => {
it('adds two numbers together correctly', (expected) => {
element(by.css('input1')).sendKeys(1);
element(by.css('input2')).sendKeys(2);
element(by.css('button')).click();
var result = element(by.binding('result')).getText();
expect(result).toEqual(3);
}); });

In this code, we're using Protractor's by and element functions to select elements on the page. We're then using the sendKeys and click functions to simulate how a user would interact with the calculator. Finally, we're using the getText function to get the value of the result binding. This is the value displayed on the screen after the add function is executed.

Again, we're using the expect function to verify that the correct result is returned.

You can run your tests using Karma or Protractor. To do this, you'll need to install these tools first. The instructions for doing so are beyond the scope of this article, but you can find them in the documentation for each tool.

Once you have Karma or Protractor installed globally, you can run your tests using the following command:


karma start my-test.js

or


protractor my-config.js

Replace my-test.js with the name of your test file, and replace my-config.js with the name of your Protractor configuration file.

Both Karma and Protractor will run your tests and output the results to the console. You can also generate a report that contains more detailed information about the results of your tests.


import { by, element } from 'protractor';
//Unit Test
describe('add', () => {
it('should add two numbers', () => {
expect(1 + 2).toEqual(3);
});
});

// End-To-End Test
describe('login', () => {
it('should login the user', () => {
element(by.css('.username')).sendKeys('test');
element(by.css('.password')).sendKeys('test');
element(by.css('.submit')).click();
expect(element(by.css('.message')).getText()).toEqual('Welcome, test!');
});
});

Conclusion

Testing is an essential part of the software development process. Unit testing and end-to-end testing are both necessary, and there are several different tools you can use for each type of testing. In this article, we've looked at some of the best options for Angular testing. You can use these options as per your preference and requirement.

Angular Testing FAQs

1.What is the most critical component of Angular testing?

The TestBed is the essential testing part of Angular testing. The TestBed creates a dynamic Angular test module that mimics an Angular @NgModule. 

2. Can Selenium be used along with Angular?

Selenium API is implemented in multiple major programming languages, allowing you to write tests in Java, C#, Python, Ruby, JavaScript, etc. If you already have a Selenium-based end-to-end testing framework, you can use it to test AngularJS web applications.

3. What are the challenges in automating Angular?

Synchronization and the lack of AngularJS-specific locating strategies, such as ngmodel, ngrepeater, ngbinding, etc., pose the greatest obstacle to automating an AngularJS application using Selenium.

4. What is the use of NgWebDriver?

NgWebDriver can be used as a tool in Selenium to handle the challenges mentioned above. It is a small Java library comprising web driver locators and more Angular for Java. It supports Chrome, Firefox, and all other Selenium WebDriver browsers.