About code coverage

Now we’ve explored the different test types, you probably want to start writing tests right away. But before you put this book away to get coding, let us finish this chapter with the question of how much of your code you should test.

A part of the answer lies within the concept of code coverage, which we already briefly mentioned in Chapter 8, Code Quality Metrics when we talked about code quality metrics. Let us have a closer look at it now.

Understanding code coverage

Code coverage measures the proportion of code that is covered with tests. The higher the code coverage, the better—if there are more tests, the software is less likely to contain bugs, and it will be harder to introduce new ones unnoticed. Higher code coverage is also a possible indicator of better code quality—as we discussed in a previous section of this chapter, tested code must be written in a certain way, which usually leads to better quality.

Generally, the...