TDD for today's engineering teams: Test Driven Development

Posted by
Nate McGuire in Development category

Test-driven development (TDD) is a software development process that involves writing automated tests before writing the actual code. It is an approach that focuses on ensuring the reliability of code and improving the overall software quality. In this article, we’ll explore what TDD is, its pros and cons, and popular TDD approaches for Laravel, Ruby on Rails, and Swift.

What is TDD?

TDD is a development process in which developers write automated tests before they write the actual code. The idea is to create small tests that cover a specific feature or function of the software, and then write the code that satisfies those tests. The process involves the following steps:

  1. Write a test that describes a feature or function.
  2. Run the test to see that it fails.
  3. Write the code to make the test pass.
  4. Refactor the code to improve its quality, and then run the test again to ensure that the changes didn’t break any existing functionality.

What are the pros and cons of TDD?

Like any development process, TDD has its pros and cons. Here are some of them:


  • Tests act as documentation for the code.
  • Tests provide immediate feedback on code changes, making debugging easier.
  • Tests help identify bugs early in the development process, saving time and money in the long run.
  • TDD encourages better code design and modularity.


  • TDD can be time-consuming, especially in the beginning.
  • It requires a mindset shift for developers who are used to writing code first and testing later.
  • TDD can lead to over-testing, where developers write too many tests for a feature, making maintenance more difficult.

Examples of code writing using TDD

Here’s an example of how TDD works in practice:

Let’s say we’re building a simple calculator application. We would start by writing a test for the add function:

test('it adds two numbers', () => {
expect(add(2, 2)).toEqual(4);

We then run the test, which will fail because we haven’t yet written the add function. We then write the function to make the test pass:

function add(a, b) {
return a + b;

We then run the test again, and it should pass. We’ve now created a working add function and have ensured that it works as intended.

Examples of Libraries or open source TDD tools

There are many libraries and open-source TDD tools available that can make the process of writing tests easier. Here are a few examples:

  • PHPUnit: A popular testing framework for PHP that provides a range of features for writing unit tests.
  • Jest: A JavaScript testing framework that provides a simple and intuitive API for writing tests.
  • RSpec: A testing framework for Ruby that allows developers to write tests in a human-readable format.
  • Quick: A Swift testing framework that allows developers to write tests using a concise, easy-to-read syntax.

Popular TDD approaches

Advantages of TDD

  1. Better Code Quality: As developers write test cases before writing code, the code produced is usually of better quality, modular and easy to maintain. This is because developers are forced to think more about the design of the code before writing it.
  2. Reduced Debugging Time: TDD helps identify defects earlier in the development cycle, making it easier and faster to debug. This saves developers a lot of time and effort, as fixing bugs at the later stages of development is more expensive and time-consuming.
  3. Faster Development: While TDD may initially slow down the development process, it saves time in the long run. As developers write tests first, they are able to detect issues early on and prevent regression. This reduces the time required for fixing defects, and enables faster development cycles.
  4. Improved Collaboration: TDD helps promote better collaboration between developers, testers and other stakeholders. By writing tests first, developers and testers can have a better understanding of the requirements, and can work together to ensure that the code meets the specifications.

Disadvantages of TDD

  1. Additional Upfront Time Investment: TDD requires developers to write test cases before writing the code, which can initially seem like a waste of time. However, this time investment pays off in the long run by reducing debugging time and increasing code quality.
  2. Additional Overhead: TDD requires developers to maintain test cases alongside the code, which can be an additional overhead for the team. This requires additional time and effort to ensure that the tests are up to date and that they cover all use cases.

Examples of Code Writing Using TDD

Here is an example of how TDD can be used to develop a feature:

  1. Write a test case for the desired feature.
  2. Run the test case and ensure that it fails.
  3. Write the code required to make the test pass.
  4. Run the test case again and ensure that it passes.
  5. Refactor the code to improve its design and maintainability.
  6. Repeat the process for the next feature.

Libraries and Tools for TDD

There are many libraries and tools available for TDD across different programming languages and frameworks. Some of the most popular ones are:

  1. JUnit for Java
  2. PHPUnit for PHP
  3. RSpec for Ruby on Rails
  4. XCTest for Swift
  5. PyTest for Python

Popular TDD Approaches by Language

While the basic principles of TDD apply across programming languages, the specific approaches used may vary depending on the language and framework being used. Here are some popular approaches for TDD in several languages:

Laravel (PHP)

In Laravel, developers often use PHPUnit and Mockery for TDD. Tests are typically organized into three types: unit tests (for testing individual methods), feature tests (for testing user-facing functionality), and browser tests (for testing browser interactions).

Ruby on Rails

RSpec is a popular TDD tool for Ruby on Rails, with Capybara used for integration testing. Tests are often organized into three types: model tests (for testing database interactions), controller tests (for testing controller logic), and feature tests (for testing user-facing functionality).


In Swift, Quick and Nimble are commonly used for TDD. Tests are often organized into two types: unit tests (for testing individual methods) and integration tests (for testing the interaction between multiple components).

Incorporate TDD into your software development workflow

Test Driven Development (TDD) is a powerful technique that can greatly improve the quality and reliability of software. By writing tests before writing the code, developers can ensure that the code meets the requirements and functions as intended. TDD also provides the benefit of catching errors early in the development process, which can save time and resources in the long run.

While TDD may not be suitable for all projects or all developers, it is definitely worth exploring and experimenting with. There are many libraries and open source TDD tools available, such as JUnit for Java, RSpec for Ruby, and XCTest for Swift, that can make it easier to implement TDD in your development workflow.

When it comes to popular TDD approaches for specific frameworks, Laravel, Ruby on Rails, and Swift all have their own unique approaches. For Laravel, developers often use PHPUnit and Mockery to write tests that ensure the application functions as intended. For Ruby on Rails, RSpec and Capybara are commonly used to test the application from both a user and developer perspective. In Swift, XCTest and Nimble are often used to write unit tests that ensure the code functions as expected.

Overall, Test Driven Development is a technique that can greatly benefit software development teams, as long as it is used appropriately and integrated into the development process in a thoughtful and intentional way. By prioritizing quality and reliability through TDD, developers can build software that meets the needs of their users and stands the test of time.

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