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What Is Test-Driven Development? TDD Guide For Beginners

It’s inevitable for mistakes to happen during the software development lifecycle – developers are human and everybody makes mistakes. But that doesn’t mean you want them to happen. Going all-in on a project only to discover a bug or oversight after the fact can be incredibly demoralizing.

While you may not be able to completely eradicate the possibility of making errors, you can minimize their occurrence. One of the best ways to do this is through test-driven development. 

So, what is test-driven development, and how does it work? In this article, we’ll answer both of those questions and more by diving deep into the topic of TDD and the value it offers to the development process.

What Is Test-Driven Development?

Test-driven development (TDD), sometimes referred to as test-driven design, is a software development strategy that involves methodically testing code and fixing any errors or oversights before the actual coding begins. This style of programming is almost like a double-check system, where developers test their code to make sure that it is as bug-free and efficient as possible.

Rooted in agile and extreme programming, TDD involves writing tests for every feature or line of code before it is written. It’s all about satisfying the answers of whether the code will work as expected in various use cases, which are iteratively built and tested one at a time. 

TDD is an alternative to strategies that aim to create ‘optimum solutions’ in the first pass, instead encouraging developers to focus on incrementally improving the code by using a cycle of writing tests, writing the code, and repeating. The ultimate value of this process is that it ensures developers are taking the time to think about how their code will be used and identify any issues before they become major problems.

Test-driven development follows three main principles/rules:

1. You should not write any production code unless it is intended to make a failing unit test pass.

2. You should not write any more of a unit test than is needed to fail (compilation failures count as failures).

3. You should not write any more production code than necessary for passing the one failing unit test.

Why Use Test-Driven Development?

The main reason developers choose to use test-driven development comes down to one word: quality.

In the world of coding, quality can make or break a project’s success. It’s the difference between functionality and failure, and between users having a great experience or abandoning your project. TDD’s core goal is to help developers maintain high quality, ensuring that their code works as intended. Testing is a web development best practice and is helpful in finding and resolving issues before they become more serious.

What Are the Benefits of Test-Driven Development?

While test driven development can seem tedious at first, there are some serious benefits to using it during the software creation process. Below are just five examples.

  • TDD Can Actually Save You Time: While test driven development may require a bit of extra work upfront, it undoubtedly saves you time from manual testing later down the line. Since you’ve already done the work of testing, you’ll find that debugging is much quicker and easier.
  • Continuous Delivery: The continuous delivery aspect of TDD is incredibly useful for developers and teams working on a project. It allows them to quickly fix errors and add new features without compromising code quality.
  • More Robust Code: Test driven development helps you create more robust, reliable code. Because TDD tests are written before the code is written, it helps developers think through all possible scenarios and create a more comprehensive final product.
  • A More Flexible Codebase: By using TDD, developers are forced to think about their code from all angles. This encourages them to create more general and flexible solutions that can be adapted for future use cases.
  • Easier Onboarding/Maintenance: By using test driven development, developers are creating code that is high quality and easy to maintain. This makes onboarding and maintenance much simpler and more efficient.

Test Driven Development Process: 5 Steps

The test driven development process consists of five steps that developers follow and repeat until the software is complete. Here’s an explanation of each and what’s involved:

  1. Write a Test

Write test code that defines a function or improvement that you want to make in the code. The test should be written before any coding is done, as it will define the code that needs to be written.

  1. Run All Tests & See the Test Fail

Once the test is written, you can run all the tests in your suite to make sure that the one you just wrote fails. This will confirm that it works properly.

  1. Write Code to Pass the Test

Once the test fails, it’s time to write the code that will make the test pass. This step is all about writing and testing until you get the desired result.

  1. Confirm the Test Passes

After the code is written, run all of your tests again to make sure that the one you just wrote now passes. If it doesn’t, you will have to go back and tweak the code until it does.

  1. Refactor the New Code

The final step is to refactor the code you just wrote and rinse-and-repeat the process. This involves repeating Steps 1 through 5 until all the desired tests have been written and passed.

The Three Phases of the TDD Cycle

The test driven development cycle follows three phases, each of which is essential for the successful completion of a software project. Known as the Red, Green, and Refactor phases, these are the defining sequence of TDD:

  1. Red Phase

The Red Phase is when you write a test that fails, ensuring that your coding works as intended. Failing tests provide valuable information and should be welcomed, as they indicate that the test is working properly.

  1. Green Phase

The second phase is the Green Phase. During this step, you write the code that will make the test defined in the Red Phase pass. You should take care to ensure that the code you write is clean, concise, and effective.

  1. Refactor Phase

The final phase of TDD is the Refactor Phase. During this step, you can modify and refactor the code you have written to be more efficient and easier to read. This is a great way to make sure that your code is efficient and maintainable.

Is Test Driven Development Worth It?

While not everyone uses test driven development, it is widely considered to be a beneficial practice and a worthwhile investment of time. TDD has been proven to help reduce bugs, improve the overall design of code, promote iterative processes, and encourage better software development practices.

TDD also helps developers to rapidly detect any new bugs that may have been introduced due to changes in the code, which can save time and resources in the long run. It also encourages developers to think more critically about their code and take the necessary steps to ensure that it is as efficient and reliable as possible.

There’s definitely a learning curve to getting started with Test Driven Development, but once you get the hang of it, the process is ultimately straightforward and could end up saving you tons of energy, time and money.

Whether or not it’s right for you will come down to the question of your willingness to learn new practices, but it’s certainly worth considering. If you plan on working on a project that requires the utmost confidence in quality and reliability, taking the time to learn and use TDD now could be well worth the effort.

Learn Programming at Coding Dojo

Getting started with test driven development may be intimidating – but it doesn’t have to be. With the right educational support and resources, anyone can learn the principles of TDD and apply them to their projects.

Coding Dojo is a leading provider of web development and programming education, offering a variety of courses to help aspiring developers get ahead in their chosen career path. Our full-time and part-time software development boot camps are perfect for those looking to learn the fundamentals of software engineering and test driven development in a real-world environment.

Over 14 weeks, our experienced instructors will guide you through TDD, as well as help you understand the principles of Object-Oriented Programming, coding best practices, and more. The skills you’ll learn here will open up doors to a new world of possibilities, and help you build the confidence and know-how necessary for success.

So – what is test driven development? Now you know. If you’re interested in learning more about TDD and how it can benefit your workflow, we invite you to join us at Coding Dojo and take advantage of our expert instruction. You’ll get the skills and knowledge necessary to transform your career—and your life! Apply to a coding bootcamp today