October 11, 2022

How to Do Angular Unit Testing and Why?

Testing each feature (also known as a unit) is critical to guarantee that every function in the program functions as planned. In testing, evaluating a particular capability vs. a whole program end-to-end is pretty different. Unit testing comes into play at this point.

Angular is an open-source, TypeScript-based JavaScript framework. Since JavaScript is a powerful programming language used to construct online apps, it is vital to understand how to do unit testing in JavaScript. This article will explore how to conduct these tests, what to use, and why.

What is Angular?

Modern websites use the computer language JavaScript (JS), which offers numerous interactive elements with which consumers are acquainted. Web developers often depend on client-side JavaScript frameworks for functionality and to keep websites and online assets working correctly.

Angular is a technology that provides the means to develop a web application, aids in the design, and organizes the underlying code. In 2010, Google released the JavaScript framework known as AngularJS. It contains a feature that facilitates developers’ creation of rich, single-page apps. The name of subsequent versions of AngularJS is shortened to Angular.

Significant organizations have used Angular to build applications, several of which have become mainstream brands. Such as-

  • Gmail
  • Youtube TV
  • Paypal
  • Wix WebApps
  • Microsoft web
  • Upwork
  • Freelancer

Why should you test Angular Apps?

Validating an Angular codebase function by function is the most effective approach to enhance code quality, have fewer defects in production and less dead code, minimize maintenance costs, and accomplish quicker refactoring and even upgrades without inconsistencies damaging the whole system.

Initially, it may seem slow, but it pays off in the long run. Throughout the development process, bugs are identified and fixed. The procedure for debugging is enhanced. If a particular test fails, it is simple to determine precisely what is not operating as planned. And while test-driven development and unit testing, in particular, seem more complicated, leveraging new test automation platforms and best practices can significantly simplify and automate the whole process.

What is Unit testing?

Unit testing is one of the methods of automated testing. Unit tests exercise tiny portions of an application in total isolation and compare their actual behavior to the intended behavior. The phrase “full isolation” refers to the fact that unit-testing angular applications are not linked to external dependencies such as databases, the filesystem, or HTTP services. This enables unit tests to be more reliable and rapid since they will no longer fail due to difficulties with external services.

Unit tests are produced using code. You may think of unit tests as little programs that exercise your application by interacting with small sections. Each unit test is akin to describing or illustrating how a unit operates in a particular circumstance. By conducting the suite of tests, developers may get instantaneous feedback after modifying a codebase.

Why should you do Angular unit testing?

Typically, developers build unit tests first, followed by the actual program code. Test-driven development describes this methodology (TDD). In TDD, the requirements are converted into particular test cases, and the program is subsequently enhanced to pass the new angular tests. Unit tests let the changing of code without impacting the functioning of other units or the program as a whole. This saves resources by making it more straightforward for developers to identify faults at this stage.

Additionally, inside unit test environments, the modules of a product become segregated from one another and have their area of responsibility. In this circumstance, testing is more trustworthy since they are conducted in a confined setting. Due to this stability, the code becomes dependable as well.

Along with the facts mentioned above, let’s examine the many advantages of unit testing.

  • Unit tests assist in locating and resolving issues sooner. Organizations that implement unit testing into their development process and begin testing as early as feasible in the software’s lifetime can find and fix problems more quickly.
  • Your unit test suite serves as a safety net for developers. A thorough suite of unit tests may serve as a safety net for developers. By periodically executing the tests, they can ensure that their recent alterations to the code have not damaged anything. In other words, unit tests aid in avoiding regressions.
  • Unit tests may help improve the quality of code. This item follows naturally from the preceding article. Because unit tests serve as a safety net, developers are more confident when modifying code. They can restructure the code without worrying about breaking anything, enhancing the codebase’s overall quality.
  • Unit testing can help to improve application architecture. Adding unit tests to a codebase often indicates a high-quality application design. Therefore, the need to produce testable code may motivate improved design. This is why TDD (test-driven development) is so efficient.
  • Unit tests can be utilized as documentation. Unit tests provide examples of how to use the code being tested. Consequently, you may also think of them as executable documentation or specs.
  • Identify code smells in your codebase. Having difficulty generating unit tests for a particular piece of code indicates code smells, such as too complicated routines. If the simplicity with which unit tests can be added to a codebase is a positive indicator, the converse is also true.

How to Conduct Unit Testing in Angular & Test Angular Components

When designing tests for components, ensure that all of these behaviors are considered.

  • In the HTML DOM structure, they can render templates.
  • They can receive data from their parent components through Inputs and output data via Outputs.
  • They can respond to several sorts of situations.
  • They can communicate with retailers or services.
  • They can bind data and make it editable for the user.

Set up TestBed

Angular offers TestBed for testing, which establishes an environment where components and services can be readily validated and verified. It is like a standard Angular module, and all stated features are compiled. Utilize the beforeEach method to avoid duplicating code in every test.

Testing the DOM

Most of the time, component functions implement logic reflecting the template. Using DebugElement’s query and queryAll methods, we can get access to the DOM tree:

  • the query returns the first element that suits a criterion.
  • queryAll returns an array of matched entries 

Triggering event handlers

There are two options for tests. The first option is to execute the function directly, while the second option, which is recommended, is to implement a click on that button. Using the trigger event handler property of DebugElement makes this simple to do. It contains two arguments: the name of the event and its characteristics.

Tools for angular unit testing

Jasmine: The Jasmine testing framework may be used to test JavaScript code. Specifically, it is a framework for BDD (Behavior-Driven Development). Due to its straightforward syntax and the fact that it does not need a DOM or rely on other frameworks, Jasmine is easy to use right out of the box. Jasmine is the default testing framework that the Angular manual recommends. The Angular CLI automatically configures Jasmine, so you do not need to install it individually.

Karma: Angular’s default test framework is Karma. The AngularJs team developed it because they had difficulty in Angular testing using the available tools at the time. Karma enables you to test your apps on actual web browsers and devices, such as tablets and mobile phones. It is also very adaptable since it is compatible with other testing frameworks. Angular’s default framework is Jasmine (which we’ll discuss in a moment), but you may change it with Mocha, QUnit, or others. In addition, integration with continuous integration systems like Travis, Jenkins, CircleCI, and Semaphore is simple.

Protractor: Protractor is an end-to-end testing instrument for Angular apps. It executes your tests in a real browser and replicates the user’s interaction with your application.

Angular CLI: The Angular CLI (Command Line Interface) is a tool that can be used to construct, develop, and test Angular applications.

Angular Unit Testing Best Practices

Here are some things to follow while performing angular unit testing:

  • Tests should be quick and straightforward, necessitating test cases to be executed faster since this fulfills the aim of unit testing. If the angular test cases are too sluggish, developers will not implement them as often as they should—moreover, the more straightforward the unit test cases, the more precise the test findings.
  • Test cases should not repeat the logic of the implementation.
  • Test findings will be neither predictable nor precise without exposure to natural production settings (real, working devices). The behavior of test cases should be deterministic so long as their code remains constant. For tests to remain deterministic, quality assurance personnel must conduct them on actual browsers and devices, not emulators and simulators.
  • Consistently execute unit tests in a sandboxed environment, removing any external dependencies.
  • Utilize spies from the Jasmine framework while testing service dependencies.
  • When testing components, it is preferable to access the DOM using debugElement (which provides an abstraction for the primary runtime environment) rather than the native element.
  • If your app is on a server, use By.css instead of queryselector since the latter is browser-only.
  • Ensure that at least 80 percent of the code is covered.
  • Implement an efficient naming scheme for the test cases


Unit testing is a necessary form of automated testing; some experts even argue that it is the most vital. This stands for all programming languages and platforms, including JavaScript. Whether you’re using JavaScript in the backend, a front-end framework, or writing vanilla JavaScript, unit testing is required.

There are multiple tools available for each sort of testing. Choose a gadget, such as HeadSpin, that provides the most advantages and meets your budget for every kind of testing.

About the author 

Kyrie Mattos

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