You have consistently written unit tests and you have a line coverage of, let us say, 80% and all of your tests pass. Pretty good, isn’t it? But then you change your code and still all of your tests pass although you have changed code which is covered by your unit tests. In this post, we will take a look at mutation testing which will test the quality of your unit tests.
Introduction
We value our code quality very much. We execute static code analysis, we write unit tests, integration tests, etc. We can set minimum threshold values for certain metrics: we do not allow critical, major analysis issues, all tests must pass, etc. These are all good and valuable items to check in the pipeline to ensure a certain quality level. But what is the value of the metric itself?