Unit testing coverage is a great way to show us the amount of tested lines and branches of code, but is this really enough? The answer is "no" since unit testing coverage does not really fully measure the efficiency of the unit tests.
This is why there is a need for having techniques that show unit tests efficiency. Mutation testing is one of these powerful techniques. The main idea of mutation testing is to perform byte code modifications (mutations) to original Android app source code and then run app unit tests to check if they are strong enough to fail as a result of these mutations.
This session discusses mutation testing techniques, and demonstrates PIT as a powerful mutation testing tool for Android apps with demos.