How to measure Groovy code coverage when executed from Java at runtime (via ScriptEngine)?

I'm very new to test coverage, and have so far found intellij's automated testcoverage to be more than adequate. But I'm struggling to figure out how to go about extending my coverage to groovy scripts.

Basically in my java code I use ScriptEngine to process a string representation of a groovy script.

ScriptEngine engine

engine.eval(groovyAsString)

Any pointers in the right direction would be greatly appreciated :)