We can’t upgrade from Groovy 2.1 because of rather peculiar bug (seems to be in Jacoco, but may also be in the Groovy codegen): https://github.com/jacoco/jacoco/issues/200
It seems to happen only for TestNG tests (not JUnit), with test classes written in Groovy (not Java), when using Groovy 2.2 (not 2.1) and they call specific Java code constructs like static factory method.
I am curious whether anybody else has had the problem.