I have come across a very strange phenomenon:
Our CI system (Jenkins with Maven and Sonar plugin) runs Maven test builds on checkins (works fine) and runs nightly builds with Sonar intgration (ran fine until last week). Now the nightly build compiles and runs the test (all green) and calls the Sonar plugin. After the static analysis the Sonar start JaCoCo to measure the until test coverage; when JaCoco runs the unit tests (again), a lot of them run through as expected, but then first one test throws an exception (not thrown in the usual runs) about creating an object that is already there, and some tests later the whole process freezes in the try to rollback a transaction (normally not rolled back).
No component has been updated, and no suspicious code changes have been done around the failing tests.
Does anybody know, how JaCoCo treats the unit tests differently and how to solve this problem?