In the IT world, it is often observed that software developers and testers use the terms "code coverage" and "test coverage" interchangeably. Although both terms are used in relation to coverage measurement, they refer to two different things. Incorrect use of these terms can lead to misunderstandings and incorrect conclusions, which may result in flawed decisions and, consequently, lower quality software.
If you want to avoid this mistake and are curious about the exact difference between code coverage and test coverage, then this article is for you.
What is test coverage?
Test coverage is a method that helps determine how thoroughly the testers have tested the code or features during the development process. It shows the proportion of tested parts to all possible parts. A high test coverage ratio means that the testing extensively covers a significant portion of the code or features. This has many benefits, including helping to identify errors early in the development process, thereby largely preventing the end user from encountering improper functionality. Test coverage examination also helps testers identify areas that need further testing and allows developers to focus on critical areas and address deficiencies in a timely manner.
What is code coverage?
Code coverage is an important metric in software development that provides information on how much of the code is touched by tests. When using it, we must keep in mind that code coverage analysis is only for validating test cases run on the source code, not for evaluating the software product. Moreover, it does not show whether the source code is error-free or ensures the correctness of the written code.
Why is it important to monitor the code coverage metric? Continuous analysis of this metric helps developers understand bad or unused code. As a result, they can improve coding practices, which in turn leads to better product quality and maintainability.
Furthermore, this metric helps developers complete the software development process faster, thereby increasing their productivity and efficiency. As a result, companies can deliver more products in a shorter time, undoubtedly leading to increased customer satisfaction and a higher return on investment.
Difference between test coverage and code coverage
We have demonstrated that test coverage and code coverage are two distinct concepts in software development. In summary, test coverage shows how thoroughly we have tested the software. On the other hand code coverage shows how much of the code is covered by tests.
What does this mean in practice? Suppose we are working on developing a web application. Test coverage indicates how much the tests cover a process within the entire web application, such as the registration process. If this process is thoroughly tested, the test coverage ratio will be high. On the other hand, code coverage shows how much of the registration process code is covered by tests. So, if only half of the registration process code is tested, the code coverage will be low, even if the test coverage is high.
Which metric should be monitored during the development process?
After gaining a better understanding of the two concepts, the question may arise as to which should be monitored during the software development process. Since they are completely different measurement approaches, it is not justified to choose one over the other. Code coverage is a quantitative metric and is more related to white box testing techniques. Meanwhile, test coverage is a qualitative metric and approaches from a black box testing perspective.
There is no correct answer to the question posed; it entirely depends on the business requirements of the enterprise and the complexity of the software application. However, in most cases, it can be said that it is worthwhile to monitor both test and code coverage.