Eclipse's ability to debug and run a single failing unit test were massive as well. IntelliJ was always hit or miss as to whether it would allow you to run a subset.
IntelliJ refactorings also were a lot less smart IMO - often trying to refactor unrelated comments and sometimes code that was unrelated but happened to be named the same thing.
I don't mean to sound rude here, but that just sounds like nonsense to me. How are you supposed to run code that won't compile? Does eclipse just generate random bytecodes for the party that doesn't compile?
> debug and run a single failing unit test
I'm not sure where the issue is for you, but this has always been available since I have used IntelliJ, going back 15 years.
https://www.eclipse.org/jdt/core/
> An incremental Java compiler. Implemented as an Eclipse builder, it is based on technology evolved from VisualAge for Java compiler. In particular, it allows to run and debug code which still contains unresolved errors.