Getting Started with Test-Driven Development in Angular

Introduction

Test-Driven Development (TDD) is a software development process widely used in

Angular development to ensure code quality and reduce the time spent debugging. TDD is an agile approach to software development that emphasizes the iterative writing of tests before writing the actual code.

In this article, we'll take a look at how to serenely build an application based on the Test-Driven Development approach.

We'll start with a brief look at the process of developing an application without TDD, then use the Test-First approach to better understand the benefits of TDD, and finish with a case study on cart processing in an e-commerce application, for example.

Developing an application without using Test-Driven Development?

 When we generally develop an application without using TDD, this is how we proceed:

• First, we write the source code;
• Next, we write the test corresponding to the source code;
• And finally, we refactor our code.

As we evolve, we find it hard to detect and manage bugs in our application, because we always manage to write the tests to satisfy our code. As a result, we don't manage all the test cases we need to, and our application is very sensitive to the slightest modification. It's very easy to get regressions.

In the next section, we'll look at how to develop an application using the Test-First approach.

Developing a Test-First application?

 Developing an application using the Test-First approach means writing the tests before writing the source code, as the name indicates. Here's how we do it:

• Write the exhaustive tests related to the feature we want to implement;
• Then write the code associated with the tests;
• Finally, we refactor the code.

Using this approach, we are constrained to have an exhaustive vision of the features to be developed on our product, which means we can't evolve in an agile context. If tomorrow's features need to evolve or be completely modified, we'll have a very difficult time updating our source code. Also, we'll be very slow in developing features, because we'll have to write all the possible test cases before we start writing the associated code.

Now that we've seen these two approaches, in the next session we'll move on to the main topic of our article, the Test-Driven Development approach.

Getting started with Test-Driven Development methodology

Test-Driven Development is a dynamic software development methodology that prioritizes the incremental creation of tests as minimalist code is implemented, while conforming to the User Story. In this section, we’ll explore the role of TDD in application development, then we’ll discover the core principle of TDD and the tools needed to successfully implement this approach.

What role does TDD play in application development?

TDD plays a crucial role in improving software quality, reducing bugs, and fostering better collaboration between developers and QA teams throughout the development process. We can summarize its role in three major points:

• Quality: TDD guarantees high test coverage, so that bugs can be detected quickly and high-quality code maintained.
• Design: By writing tests upstream, we think about the architecture of our code and obtain a clearer, more maintainable design.
• Agility: TDD favors incremental and iterative development, making it easier to adapt to changing needs.

In this section, we’ll discover the core principle of TDD.

What is the core principle of TDD?

The TDD approach is based on a cycle known as the red-green-refactor cycle, which forms the core of this approach. Here's how it works:

• Write a test before coding: We start by defining a small piece of functionality and writing a test that will fail until that functionality is implemented. We don’t need to write the exhaustive tests related to the feature.
• Just the right minimalist code: We then write the minimum code necessary for the test to pass.
• Refactor: Once the test has been passed, the code is improved without changing its behavior.

In the next section, we’ll learn the tools needed to successfully implement this approach

Tools for Test-Driven Development

Case study: << Managing a shopping cart on a sales site. >>

In this case study, we’ll implement some features about management of a shopping cart. The goal is very simple. Given a developer, your task is to develop the shopping cart of a sales site using a Test-Driven Development approach. We’ll do it step-by-step following the principles of TDD.

When we’re asked to implement the shopping cart on an e-commerce application, we’ve to stay focused on the application and ask ourselves the right questions to find the most basic scenario when a customer lands on the shopping cart page. In this scenario, the shopping cart is empty by default when a customer launches your application. So, we’ll follow these steps about our first-ever scenario:

• Write the test on the assumption that the customer's shopping cart is empty at initialization (the most basic scenario):

• Write the minimal code associated with the test:

• Refactor the code if necessary:

We don’t need a refactoring in our case.

Now, we can continue with our second scenario. Once we’re satisfied that the basket is empty when the application is launched, we’ll check that the total cart price is 0. We’ll follow the principles of TDD and stay iterative on our code.

• Write the test to calculate the total basket price when the basket is empty:
• Write the minimal code associated with the test:
• Refactor the code if necessary.

Conclusion

Test-Driven Development (TDD) is a powerful methodology that enhances code quality, fosters maintainable design, and promotes agility in software development. By focusing on writing tests before code and iterating through the red-green-refactor cycle, developers can create robust, bug-resistant applications. In this article, we’ve explored the differences between traditional development approaches and TDD, delved into its core principles, and applied the methodology in a practical e-commerce case study.

For a deeper dive into mastering TDD in Angular, consider reading Mastering Angular Test-Driven Development by Ezéchiel Amen AGBLA. With this book, you’ll learn the fundamentals of TDD and discover end-to-end testing using Protractor, Cypress, and Playwright. Moreover, you’ll improve your development process with Angular TDD best practices.

Author Bio

Ezéchiel Amen AGBLA is passionate about web and mobile development, with expertise in Angular and Ionic. A certified Ionic and Angular expert developer, he shares his knowledge through courses, articles, webinars, and training. He uses his free time to help beginners and spread knowledge by writing articles, including via Openclassrooms, the leading online university in the French-speaking world. He also helps fellow developers on a part-time basis with code reviews, technical choices, and bug fixes. His dedication to continuous learning and experience sharing contributes to his growth as a developer
and mentor.