jboner/akka — comment on commit 57de4c969c59f7b726e08fe260a0596385399cb5
File: akka-testkit/src/main/scala/akka/testkit/TestKitExtension.scala line 20
By viktorklang:

Then I think it should be:

def registerExtension[T <: AnyRef](key: ExtensionKey[T], ext: Extension[T]): Extension[T]

So that you can check:

val ext = ...
if(ext != registerExtension(key, ext)) alreadyRegistered else awesomized