How do you measure code coverage and quality in TDD?

Today, multiple software applications offering the same functionalities are available. Therefore, you must serve an excellent software application to reach a large audience and stand out. Test-driven development is the best way to develop excellent and reliable software applications. This is due to its unique development technique. In TDD, every functionality of the software application is separately developed and tested. Also, the test script is designed before development. Therefore, if the test case fails, new code is written. It is best suited for Test automation.

For test-driven development (TDD), we have a framework that notifies the developers to rewrite the code when the automation test fails. In simple words, test-driven development design and develop a feature. Test those features separately and rewrite the code if it fails.  It eliminates the problem of code redundancy. In other words, test-driven development is the development and execution of automated tests before the actual development of the software applications.

Here, actual development refers to writing quality code with complete code coverage and then integrating all the features to develop a complete software application. Once the software application is developed, it undergoes automation testing for overall testing.

In this article, we will understand code coverage and quality regarding test-driven development. Also, we will know their usage in test-driven testing. We will also be going through the benefits of TDD with the challenges faced during their execution.

What is Code Coverage?

The effective way to test a software application is by examining each instruction in the code. Occasionally, there may be sections of code that are rarely executed and can be missed during testing. This can result in remaining errors and bugs in the software application. Code coverage assists in addressing this issue.

Code coverage is a measurement used in test-driven testing to estimate the portion of code executed during automated testing. It can be calculated based on the ratio of statements, branches, or functions that have been executed. Higher code coverage indicates testing. Code coverage helps identify lines of code that have not been tested, which may be susceptible to errors and, therefore, require testing.

There are code coverage tools that can be integrated into the automation testing framework. These tools aid in identifying lines of code, allowing testers to create test scripts to ensure thorough testing of those sections. This ensures the evaluation of the software application code and contributes to the development of a seamless software application.

What is Code Quality?

Software applications need to perform well. The performance of the software applications is measured through the quality of the code. Code quality ensures the reliability and security of the software applications. Also, the code quality ensures the proper development of critical features. Thus, code quality is critical, and testers should focus on it.

The code quality is analyzed well if it determines what it does, performs the desirable task, and follows the standard guidelines for writing code. Also, the metrics for analyzing code quality are good documentation, easily understandable, simple, and consistent. Code quality traits such as reliability, maintainability, testability, portability, and reusability determine whether the code quality is high or low. Also, program length, vocabulary, difficulty, volume, and effort required to write code determine its quality.

How to Use Code Coverage and Quality in TDD?

Code quality and code coverage are the two key elements that can help develop seamless software applications. Thus, understanding how to use them in test-driven development (TDD) is vital. Here is a systematic approach that can be used to maintain code coverage and quality.

  • Firstly, you need to understand the key principle of the TDD. You need to write the test script first and then start your development. The test scripts should be written according to the desired functionality of the software applications. Also, it should include every scenario along with the edge cases.

  • Then, you need to develop every feature of the software application individually. After a feature is developed, it needs to be tested. If the test fails, the code must be rewritten. If not, you may proceed to develop another feature.

  • TDD will require effort and time. Therefore, adopt an automation testing framework. Choose the automation testing framework per your software application programming language and environment.

  • Branch, statement, and path coverage are some metrics for code coverage. Therefore, you must align them with the objective of your software applications. There are tools available to measure them. You may integrate those tools into your automation testing framework.

  • Once done with code coverage, bring your focus to code quality. To analyze the code quality, adopt tools that check for coding standards and possible bugs present in the software applications.

  • The next step includes integrating your tools and framework into a CI/CD pipeline. It automatically executes the testing process whenever a code changes.

  • For test-driven development, you must consider unit testing. These tests are isolated and independent. Thereby focusing on every aspect of the code seamlessly.

  • To test every function independently, you must mock frameworks. These will eliminate the requirement for external dependencies or a completely integrated environment.

  • For performing TDD, your main aim should be achieving code coverage and quality. So, you need a regressively testing of your code.

  • The code should rely on the test scripts. You need to change your code until it passes the test. Also, ensure its correctness.

What are the Benefits of Code Coverage and Quality in TDD?

We now understand that code coverage and quality are important. Here is a list of benefits they possess in TDD.

  • A higher code quality and coverage enhances the reliability of the code. It means the developed software application will be reliable, too. It also ensures that software applications do not pose any issues and every critical bug is fixed.

  • TDD has its tests written first. It means defects and bugs present in the software applications will be detected early. Thus ensuring a seamless user experience for end-users.

  • The code quality and coverage allow for easy code changes. As the tests are written beforehand, unintended changes in the functionality will be easily detected.

  • Due to the code quality and coverage, maintenance of the software applications is also improved. They are now less prone to errors.

  • A higher code quality is simple and easily understandable. Therefore, it improves the collaboration between the development team.

  • It enhances the security. This is because software applications are regressively tested to improve the quality and coverage. This eliminates all the issues present with the software applications.

  • Due to excellent code coverage, the bugs are easily detected. However, the bugs are effortlessly debugged in less time due to higher code quality.

What are the Challenges of Code Coverage and Quality in TDD?

Every task has some challenges associated with it. The same goes with TDD. Here is a list of code coverage and quality challenges in test-driven testing.

  • Software applications are complex, and achieving complete test coverage is challenging. To achieve complete test coverage, you must test each statement, branch, and function of the code. But, unintentionally, certain edges may remain untested. This is because testers and developers mainly focus on critical parts.

  • In test-driven development, code changes several times. But change in code leads to modifications to several other tests. Thus increasing test maintenance overhead.

  • Since the tests are written first in test-driven development, testers emphasize writing more test cases to ensure the quality and coverage of the code. Thereby, they focus less on the quality of the test scripts.

  • Test-driven development is done by engineering every functionality of the software application separately. Due to this, integrating external dependencies becomes a challenge for testers and developers. However, there are tools available to mock these dependencies. But sometimes, they may not replicate the actual behavior.

  •  Test-driven development is different from traditional development. Due to this, developers accustomed to traditional development may face difficulty performing TDD.

  • Developers need to balance both speed and quality in test-driven development. Emphasizing one may lead to the downfall of the other.

  • There are various limitations to the tools used for analyzing the quality and coverage of the code. Also, automation testing tools have several limitations. Sometimes, they are incompatible or cannot be integrated into the specific technology or environment.

  • TDD is performed in a team.  Therefore, a consistent coding standard has to be designed. If not done so, it may lead to conflicts and misunderstandings between various team members.

However, you can always use cloud testing platforms to scale your automation testing while measuring code coverage and quality.

LambdaTest is a powerful cloud testing platform that aims to streamline and enhance the automation testing process for developers and testers. Its ability to automate complex and uncertain scenarios sets it apart, providing a reliable solution for various testing requirements.

One of LambdaTest’s key strengths lies in its AI-powered test execution and orchestration capabilities. This platform allows users to access a vast grid of over 3000 real browsers and operating system combinations. This diverse testing environment ensures comprehensive coverage, allowing applications to be thoroughly tested across various configurations.

But LambdaTest doesn’t stop at the conventional. It goes beyond that by offering advanced features and a user-friendly interface, making it an invaluable tool for tackling intricate testing scenarios. Teams can seamlessly automate tests, ensuring efficient and effective testing across browsers and operating systems. In summary, LambdaTest is a versatile ally that empowers users to optimize their automation testing processes.


Test-driven development differs greatly from traditional development, with several benefits and challenges. In this article, we have understood the key metrics of test-driven development. That is code quality and code coverage. Also, we got to know how those metrics help in TDD. We came across the challenges faced during test-driven testing.

Also, we learned the tests are scripted, and then development occurs. Therefore, it is important to balance the speed and quality of the development. If the speed is increased, the quality and coverage of the code will be hampered. Whereas if quality is emphasized, the speed needs to be reduced. This is because quality can only be ensured if every statement, branch, and function of the code is thoroughly tested, which requires effort and time. However, irrespective of the challenges, TDD is recommended. This is because it delivers a good software application that provides a seamless user experience.