Start/Test Plugin with Different Versions of IntelliJ (not build)

Hello, 

I was wondering how I can start and/or run tests of my plugins built on version X of IntelliJ against version Y at runtime. The gradle plugin lets you specify a version under the intellij { version } but this seems to control build and run 

I'm not sure if I'm doing it wrong, but it seems like it would be cool if I could build against version Y, and then have different run configurations for runIde so I could verify in a few different ways and/or versions, and/or have tests run against different versions at runtime.