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What is Test-Driven Development and How to Do It?

When building new software, one of the major concerns of developers is how to test the software to make sure that it works fine. There are many ways to test software. Most of the time, you will write some code and then create a few test cases to test the functionality of that code. That’s not a bad system, though. However, what would happen if we flipped that procedure on its head? What if we created tests first and then wrote code to pass those tests?

What is Test-Driven development?

Test-driven development is a practice in software development where you first write test cases to define the functionality of code before implementing the actual code. Simply said, test cases for each functionality are written and tested first, and if any of them fails, new code is written to pass that test.

In TDD, test cases are designed and developed for every single functionality of the software. The concept behind TDD is to correct code to pass the failed tests before writing new code. This approach helps avoid any duplicate code, as in TDD, developers write a small amount of code at a time that is only sufficient for passing the test.

TDD Vs. Traditional testing

The major difference between traditional testing and test-driven development is that in traditional testing, testing is performed at the end of the coding, whereas in TDD, testing is performed before writing the code.

TDD is basically a specification technique that ensures your code is thoroughly tested at the initial phase of the development. Moreover, TDD ensures that your system fulfills the specified requirements for it and helps to build confidence in your system.

In traditional testing, a successful test will discover one or more bugs, and when a test fails, there’s a process as you know what should be done to pass the test.

TDD focuses on production code that verifies if testing will work properly. On the other hand, traditional testing focuses more on test case design and if the test will indicate proper execution of the software to fulfill the requirements.

With TDD, you can achieve 100% test coverage for your code. Every single line of code will be tested, unlike in traditional testing.

Benefits of Test-Driven development

Improved focus on development.

The nature of TDD is to retain your focus on the specific module you are working on without jumping around other segments of code. This leads to better productivity since it reduces the switching of context. If you do so, it may leave some parts of the code uncompleted, resulting in longer development times and more bugs.

Better quality of code

Testing a piece of code insists a developer define the functionality of that code. Being able to do it easily means that the functionality of that code is clearly defined with high cohesion. If you can perform unit testing on that code, it can easily be integrated with the rest of the project. It has low coupling to other code segments around it. This low coupling and high cohesion are qualities of a well-designed, solid, and maintainable code.

Easy refactoring

Once the tests are passing, they will have your back from then onwards. Whenever you want to make sure that new changes don’t break previous code, you just have to re-run your tests. Simple enough. Isn’t it?

You can also use TDD when working with legacy code or code from another developer. Apply TDD for the new code you are going to write, and if something goes wrong, you can verify that there are issues in your code. That will save a lot of time debugging and trying to find out what has gone wrong.

This way, TDD saves plenty of time and effort for code refactoring.

Up-to-date documentation

Above all, TDD tests can serve as perfect documentation for a developer. If you want to know how a specific class or code works, you can go through the tests and find out. It is possible as when you create the test, you plan and think about how to use that class. Therefore, you can identify all the required inputs, methods, and expected output. This becomes very useful when new members are joining the project.

How to perform TDD

The basic TDD process revolves around five simple steps, which are repeated throughout the software development life cycle (SDLC). The purpose of these steps is to ensure that the code is clean and efficient while fulfilling all the functional requirements of the system.

  1. Write a test
    Since development is driven by tests, it’s obvious that the first step is to write a new test. This test should be concise and simple, testing a very basic component of a large feature.
  2. Verify that the test fails
    After the test is written, the next step is to verify that the test fails. The main goal of TDD is to make you consider the requirement of a feature or a segment of code. By confirming that the test fails prior to implementing the feature, you will be confident that the test is useful and will be needed once you write code to pass the test.
  3. Write code to pass the test
    After verifying that the test fails, you have to write code that enables the test to pass. An important thing to note here is that you should not write any extra code that surpasses the scope of the test. As we focus on writing the simplest test possible in step1, here, you have to write the simplest code possible.
    Code written in this step will seem rough and unstable. However, it’s fine since the TDD cycle encourages constant refactoring of code, signifying that your current code could change numerous times in the future.
  4. Verify that the test passes
    Once the code is written, now you have to confirm that the test passes with that code.
  5. Refactor
    During this final step, even if you have a passing test, the written code may contain some duplications or inconsistencies. That’s quite normal, and it’s important to use the refactoring step to identify those problem areas and simplify the codebase.

This process should also include constant re-running of all the past tests to ensure that you haven’t accidentally brought in any new bugs or altered something that causes a previously passed test to fail.

On top of that, there are a few rules in TDD which will make your life easier. They are as follows,

  1. Not to write any production code unless it is to pass a failing test case.
  2. Not to write any more of a unit test than enough to fail.
  3. Only write sufficient production code to pass a failing unit test.

How TDD is done in TestUp?

TestUp is a new entrance to the test automation field, and it automates the testing of all the test cases in test-driven development. With TestUp, you can design user flows as tags and continue with the development. Then, simply fill the test steps in TestUp and approve the user flow as you wish. This is a small guide on How you can do TDD with TestUp.

Wrapping Up

In the world of software development, TDD is a reliable and accurate development practice developers can use to ensure robust code throughout the entire software. More than that, it’s a way to make sure that the final product is flexible and adaptable up to a point where adding new features and ongoing maintenance can be done without impacting the overall product.

Learning how to implement TDD effectively is not an easy task. It may require time, dedication, and sometimes an entire modification to your programming mindset. However, if you achieve it, you will understand that TDD is really worth all the effort and even more.

About the Autor



Shanika is a software engineer by profession. Being a graduate in Information Technology, she has gained expertise in Web development and Software testing. She is keen to share her knowledge and considers writing as the best medium to do so. She is passionate about everything she does, but apart from her busy schedule she always finds time to travel and enjoy nature. You can reach her at

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