Gradle Custom Plugin - Functional Test

I am trying to test my custom gradle plugin using Gradle Test Kit, while doing that I am facing an issue with buildscript.configurations.classpath.find{ ...}, this returns me the functional test build script classpath which might not have my plugin and its dependencies. The need is that in my plugin code I will expand some of my plugin resources ( from plugin class path) for some processing that the plugin does, currently the Gradle Test Kit expects me to put the customManifest with all pluginClasspath entries which works fine, but when I need to do real functional test of the plugin this pluginClasspath method does not help as my plugin class path entries are not visible via build script.

Any thoughts how to fix this issue, or this is a current limitation to the functional test kit and i have to have a separate standalone project and push my deps to it for doing my functional testing.