Before releasing software onto the market, there are a lot of processes that must take place. From the start of the project to the end, good software goes through many stages of testing, retesting, and feature additions. One of the most beneficial processes used to test software is code coverage. Read on to learn more about what code coverage is, the different levels of code coverage, and find out what percentage of code coverage you should aim for as a software developer.

How is code coverage defined?

Code coverage is one of the processes through which we can discover how effectively the code functions are executed. We can test this by adding lines of code in strategic places, that report metrics back to us. In short, it is a quality assurance process that tests the effectiveness and completeness of your software.

How can I benefit from code coverage?

Though this process makes the code longer, the benefits are too great to ignore. Would you release a product without making sure it works first? Code coverage is one of the ways we can make sure your software is functioning properly. Here are some of the things you can benefit from.

• Easy maintenance - Through analysis reports, developers can determine how scalable the software is, which then helps them add new features in the future easily.

• Find bad code - Code coverage allows you to see which areas of code were not executed, or those that were executed poorly, for easy fixing and removal.

• Quantitative metrics - Seeing the test results in quantifiable numbers helps the developers see what exactly is wrong, and fix problems faster.

• Faster product completion - When you can test quickly, you can fix quickly. When you can fix the software quickly, you can release it quickly. Makes sense, right? This process helps developers increase efficiency and release times, which then allows them to move to the next project.

What’s the difference between code coverage and test coverage?

Code coverage and test coverage are often confused, or the terms are used interchangeably. However, there are some differences between these two testing processes.

Firstly, test coverage is typically done by the QA team, and it tests how much of the code is covered by tests. Code coverage is a unit testing practice, done by developers, that tests how much code is executed during testing.

So in other words, test coverage measures how many lines will be tested, and code coverage measures how much of the code actually works.

Code coverage is a white box testing technique, whereas test coverage is a black-box testing technique. White box testing determines usability, security, and improves input-output flow. The developers can see all of these processes, which also gives these techniques the name ‘clear box testing’. Black-box testing tests the functionalities of applications without the developers being able to see the process. It focuses on fulfilling the requirements set forth by the team.

Why is measuring code coverage so important?

Testing, as we know, is a core process that is crucial to good code development. But, you may not have the right testing metrics in place, be lacking tests, or know how well the unit tests actually run. Over time, testing quality may fall, and new lines of code may not be up to the standard of the previous code. Code coverage is important to resolving these issues.

Measuring coverage ensures that you have the right number of tests taking place, know how much of the code is being tested, and maintains the quality of testing over time.

How can I measure code coverage?

The measurement of code coverage is done by percentage through this formula:

Code Coverage Percentage = (Number of lines of code executed by a testing algorithm/Total number of lines of code in a system component) * 100.

Meaning, that if you have 1,000 lines of code and 600 of them are cleared through the testing process, then you have 60% coverage. Having all 1,000 lines validated means that you have 100% coverage.

Perfection may sound ideal, and though you may want to reach 100% code coverage, it is more complex than that. Reaching 100% coverage may result in lower quality code. Generally, 80% code coverage is ideal to aim for. Why? When aiming for 100%, the quality of testing is often lacking, meaning that although you’ve reached 100%, you may not be properly testing all the functions properly. 

There are many ways to test code coverage,that mostly fall into the following categories.

• Runtime instrumentation - This determines code coverage throughout the runtime sequence.

• Source code instrumentation - Adds instrumentation statements to the source code, and compiles it. 

• Intermediate code instrumentation - A new instrumented class is created by adding bytecodes to compiled class files.

There also are different levels of code coverage.

• Condition coverage - This type of coverage measures how the conditional variables are evaluated.

• Function coverage - Function coverage analyzes all of the intended functions and determines whether or not they are working properly.

• Branch coverage - This is for decision-making code, and it ensures that every branch of the decision tree is executed under the right circumstances.

• Loop coverage - Loop coverage makes every loop process in the course code execute at least one time.

• Statement coverage - Like loop coverage, statement coverage forces the source code to execute every statement in the code at least once. 

In summary, code coverage and measurement are valuable assets to your development team. It provides easy-to-use, quantitative measurements, allows for scalability and easy fixes, and saves a lot of time for developers, who are looking for bugs and redundant or dead code.

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