March 22, 2023

The Test-Driven Development (TDD) Approach 

Test-driven development (TDD) is a software development approach where tests are written before the actual code. TDD is often used in agile software development methodologies. This ensures code is working properly and minimizes the chances of errors or bugs being introduced into the codebase.

A few weeks back, our teammate Voislav Stojkoski contributed to the third CocoheadsMK meetup, when he spoke about “TDD in Swift: A risk-free take on writing bugless code?”. CocoheadsMK is a community of programmers who gather to talk about developing for the Apple ecosystem.

In this blog post, we will share his thoughts on the benefits of TDD in Swift. We will provide examples of how it can improve the development process and code quality. 

Improved Code Quality 

TDD ensures that the code is of high quality, by catching errors and bugs early in the development process. Writing tests first will ensure that the code meets requirements and specifications. At the same time, it will reduce the risk of errors or bugs into the codebase. Tests also provide a safety net for refactoring or making changes to the code, as they ensure that the code still works as intended. 

Faster Development Process 

TDD can speed up the development process. By writing tests first, developers can identify and fix errors early on, which saves time overall. In addition, tests provide a clear guide on what needs to be implemented, reducing the time spent on writing unnecessary code. As a result, developers can spend more time on writing new features, rather than fixing bugs or errors.

Improved Collaboration 

TDD can improve collaboration among developers, as it provides a common language for communicating requirements and specifications. Writing tests first ensures that all team members are on the same page. This way they all have a clear understanding of the implementation needs. Tests also provide a straightforward way to verify that the code is working as intended, reducing the need for lengthy discussions or meetings.

Easier Maintenance  

TDD makes it easier to maintain and update the codebase. Tests provide a perfect way to identify areas of the code that need updating or refactoring. They also ensure that changes to the code do not introduce new bugs or errors. In addition, tests make it easier to add new features or functionality to the code, providing a clear guide on what needs to be implemented.


Now let us look at an example of how TDD can improve the development process in Swift.

Suppose we are developing an app that allows users to create and manage a to-do list. We want to write a function that checks whether a to-do item is completed or not. Here is how we can use TDD to implement this functionality: 

Step 1: Write the Test  

We start by writing a test for the function that checks whether a to-do item is completed or not: 

to-do item test-driven development

This test creates a to-do item with the title “Buy groceries” and sets its completed status to true. We then assert that the isCompleted property of the todoItem is true

Step 2: Run the Test  

Running the test at this stage will fail, as we have not yet implemented the isCompleted property of the TodoItem class. 

Step 3: Write the Code  

We can now implement the isCompleted property of the TodoItem class: 

TodoItem class test-driven development

This code defines the TodoItem class, with two properties: title and isCompleted. The isCompleted property is set in the initializer of the class. 

Step 4: Run the Test  

We can now run the test again to check whether the code is working as intended. Running the test should pass this time, as the isCompleted


In conclusion, TDD is a valuable approach that can enhance the development process in Swift. By writing tests first, developers can catch errors and bugs early on, and ensure that code meets the requirements and specifications. TDD can result in faster development, better collaboration, and easier maintenance. The example of implementing the isCompleted property of a TodoItem class illustrates how TDD can guide the development process and improve the quality of the code. Overall, TDD can help developers create reliable and robust software that meets the needs of users.