Coding, Software Development

What is Test-Driven Development, and Why is It Important?

Written by Karin Kelley
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Updated on May 23, 2024

Multiple development and testing techniques have been developed to ensure a high-quality output with sufficient testing. Test-driven development is one such attempt. Test-driven development reconciles elements of agile development with extreme programming to ensure continuous improvement during code development.

In this article, we will explore the concept of test-driven development, the chief phases involved in implementing it, and its best practices. We will also discuss its benefits and the importance of choosing a future-ready full stack web development program that helps prepare you to enter this vibrant field.

What is Test-Driven Development?

Test-driven development (TDD) focuses on creating tests that satisfy a certain functional requirement, writing enough code only to pass those tests, and re-working that code till it completely passes the test. It is based on agile and extreme programming methodologies. The developers do not directly begin writing the entire code from start to finish. TDD helps break down the task and verify that each part of the code works well before proceeding.

For example, suppose a developer wants to build a keyboard function. They will create a test case for the first row of the QWERTY letters. They will write the code and then evaluate it using the unit test. If there is an issue with the code function or compiling, they will revisit and modify the code, which will be subjected to the unit test again. Once the test is passed, the developer will create another test for the second row of the QWERTY keyboard and repeat the process.

TDD can also be understood using an example of an educational application such as Udemy that can be used on a mobile phone. The app includes features such as profile details, selecting courses, purchasing courses, and accessing and completing them. In this case, a test case will first be built for the profile feature.

Then, the developer will write the code for the profile feature. The code is then run through the unit test to check its operation. If it passes the test, the developer moves on to the feature of selecting a course. A test case is created, and code is written to enable the user to browse and choose the course. The developer tests the code and makes changes if it fails. If it passes, the developer moves forward to the next feature.

Such an iterative process conducted in short steps ensures that each part of the code works efficiently and that bugs are not ignored until the entire code is written.

Also Read: What is White Box Testing? Definition, Types, Features, and Benefits

What Is Test-Driven Development, and Why Does It Matter?

The typical software testing method involves writing a code to a larger extent and then conducting tests on the entire code. This results in the revelation of multiple bugs and compile failures. In such a case, the developer has to go through various lines of code and rectify them. They may miss some lines, leading to repeated code failures.

Test-driven development avoids this frustration and waste of time and effort. Using TDD, the developer is forced to verify each code component and iron out the errors immediately. Thus, when they work on the next feature, they are assured that the previous code works well and will not pose any issues after the software is deployed. Thus, TDD helps put each code through a dedicated test and builds a robust code.

Test-Driven Development vs. Traditional Software Testing

Although TDD and traditional testing goals are aligned to achieve high-quality output, a deep dive into them reveals significant differences. Aspiring software developers must know these differences to make the correct choice. Let us go through some of them.

Scope of testing: Traditional testing subjects the entire system to multiple tests and evaluates all the functions together. Meanwhile, TDD chooses small chunks of code and tests them thoroughly before moving to the other parts.
Testing approach: Traditional testing is conducted at the end of code writing, while TDD is employed during the writing stage.
Process of debugging: Traditional testing examines the completed code and reveals multiple bugs throughout the code. Hence, developers must put in more time and effort to go through the code again with a fine tooth comb and debug every issue. On the other hand, using TDD, you can identify bugs in small codes and immediately rectify them, thus reducing the total number of bugs left to be remedied at the end of code completion.
Process documentation: Traditional testing consists of a detailed document that provides information regarding the procedure, types of tests, features tested, test environment, results, and remedies. Meanwhile, TDD includes information only on the specific part of the code tested, test cases, results, and modifications.
Form of testing: Traditional testing consists of one major testing stage, after which the code is revamped to rectify the errors. It may become iterative if the mistakes are not appropriately corrected or the modifications result in further failures. However, as this involves going through long codes, developers work towards minimizing the iterations. Meanwhile, TDD is a completely iterative process wherein the developers work with fewer code lines and go through them repeatedly until all the bugs are rectified and the code passes the unit tests.

Also Read: The 10 Best Software Testing Tools in 2024

Key Phases of Test-Driven Development

TDD is a pretty simple method consisting of three main phases: the red phase, the green phase, and the refactor phase. These are described subsequently.

Red phase: In the Red phase, you create a test that evaluates those aspects of your code that are most likely to fail. For example, if you are working on a website background, your red phase would be creating a test where the background does not load properly or the colors or animation do not appear as intended. This phase helps narrow down what exactly defines a good operating code.
Green phase: In the Green phase, you write the code and then run it through the test created in the Red phase. Remember the aspects you defined in the earlier phase and create concise, manageable, and efficient code.
Refactor phase: In the refactor phase, you identify the bugs that failed your code in the unit test and work towards refining the code. This phase also helps reform redundant or mergeable parts of the code.

The Benefits and Limitations of TDD

While test-driven development seems exceedingly beneficial for streamlined software development, understanding its limitations is equally crucial. Here is a quick list of its pros and cons.

Benefits

TDD helps optimize the code-creating process.
It enables a simplified addition and evaluation of features and functionalities.
Developers can assess the feature requirements early and get clarifications when required.
A continuous feedback loop is set up to help create error-free parts of code.
Unit tests help to establish the key parameters that must be satisfied by the code, based on which developers can create effective codes.
TDD covers each feature of the code, unlike traditional testing, where some features may be missed during the overall testing procedures.
TDD reduces the time wasted revisiting earlier codes and redoing them to eliminate errors.
With every part of the code sufficiently refined, the developers can confidently move to the next part and focus their attention on the code.
A manageable and flexible codebase is developed.
The quality of the deliverable is improved, enhancing customer satisfaction.
The development life cycle is reduced, and the software can be deployed much faster.

Limitations

If your code repeatedly fails a unit test, you may get stuck at a part and delay the progress of code development.
Creating individual unit tests for each code is time-intensive and requires the developer to devote the time they may otherwise use for code development.
You need to have enough expertise to write appropriate tests, without which the TDD will not serve its purpose.
TDD may not be useful in assessing the interaction of complex codes with external systems as it only focuses on small parts within a code. Further, a complex code may require traditional testing to check its overall working even after TDD is sued.
There is a chance that developers spend more time developing the tests than writing code, leading to poorly written code and significant timeline delays.
Further, if the code passes all the tests in TDD, the developers may not review it for further refining, which may result in some errors being overlooked.
TDD cannot be used by only one team member; it must be used by all team members.

Also Read: System Testing in Software Testing: Definition, Types, and Tips

Frameworks for Test-Driven Development

Frameworks refer to the suite of code libraries and tools developers use to create tests using pre-written code. They are available for multiple programming languages; you can choose them as needed. Here are some frameworks you should remember.

Junit supports test development in Java and provides annotation methods
TestNG is another Java framework that helps in efficient unit test development
NUnit and csUnit support test creation in .NET. They enable parameterized testing
DocTest and PyUnit are used for Python codes
Rspec is a framework used for Ruby-based projects
Jest and Mocha are used for TDD based on JavaScript
WebdriverIO, which supports progressive automation
Selenium, which helps with test automation

Best Practices for TDD

Here are some best practices you can follow to ensure efficient test-driven development.

Understand the software requirements and clarify your doubts before beginning the project.
Note what a test is meant to achieve, what features you want to test, and what defines ‘pass’ and ‘fail.’
Create small and manageable tests that allow easier debugging. However, ensure they are not so simple that they test only a minuscule part of the code. They should be sufficient to test a specific feature.
If possible, reuse the test code with appropriate modifications for multiple parts of the code. This will reduce the burden of writing every test from scratch.
Do not postpone the refactoring. Modify the code when you receive the test results so you are not overwhelmed by all the changes.
Avoid creating tests for complex scenarios from the beginning. Write tests that assess the code for small features and simple use cases.
Create a rapid feedback loop to enable quick feedback and fast resolution.
Implement automation in testing wherever possible. However, ensure that you look beyond automation and perform tests for features that cannot be tested using automated tests.
Follow the Red-Green-Refactor cycle consciously and ensure simultaneous documentation of the modifications made for future reference.
Utilize continuous integration pipelines to ensure consistent, regular, and automated testing.
Ensure that your tests cover all the aspects of unit testing, acceptance testing, and integration testing.

Also Read: Unlocking the Power of Collaboration with Version Control and Git

Master the Essential Web Development Skills

Successful software development hinges on flawless software or app operation. Test-driven development is pivotal in achieving this standard, employing a meticulous testing process. A comprehensive grasp of test-driven web development is imperative to streamline your testing and coding practices. Upskilling is the key to mastering this domain.

Our meticulously designed full stack web development bootcamp is tailored to refine your skills in AWS, DevOps, Hibernate, JPA, HTML5, CSS3, Java, and JavaScript. You’ll gain proficiency in utilizing tools like Angular, Docker, MongoDB, Maven, MySQL, and Jenkins. Seasoned industry experts will impart their knowledge on essential concepts such as object-oriented programming, SQL, backend and database development, version control systems, integration and deployment, and API endpoints.

Seize this opportunity to solidify your expertise and engage in industry-relevant capstone projects, paving your path in the dynamic realm of web development.