How to measure Java unit test code for each developer?

Question

Scenario: the team is working on a Java / Maven / JUnit project using some kind of SCM. We would like to increase testing coverage, that is, all developers should test the code more intensively. Measuring overall test coverage improvements using something like SonarQube is simple enough, but you need to do this for each developer to be able to recognize outliers: engineers who have better test coverage and engineers whose coverage is worse.

How would you answer the question "what is the test coverage of the code changed by developer X over the past month?" Is there a surrogate, rough measure that can be implemented more easily?

Answer 1

There is a commercial Cockpit developer plugin that does just that, as well as other great features.