How to measure Java code unit test coverage per developer?

Question

Scenario: a team works on a Java/Maven/JUnit project using some kind of SCM. We would like to increase test coverage, meaning all developers should test code more intensively. Measuring overall test coverage improvements using something like SonarQube is easy enough, but you need to do it per developer in order to be able to recognise the outliers: engineers which have the best test coverage and engineers whose coverage is worst.

How would you answer the question "what is the test coverage of code modified by developer X during the last month?" Is there a surrogate, approximate measure that could be followed more easily?

Answer 1

There is a commercial Developer Cockpit plugin that does just this, plus other nifty features.