The particular library was in the pom.xml dependency hierarchy but it was resolving to an earlier  version. Maven was switched to offline mode during the tests and I had never needed this version of the library before. This meant  that the local version of my maven repository did not have jar and maven emits it slightly unhelpful error. It would be better if it told us that it could not find the artifact and since its in offline mode, can't go and retrieve it.

There are two quick hacks. Add the library and version into the pom.xml and do a build. This will pull the library into your local repository and maven will be able to find it offline. You could also just take maven in the tests online by removing the goOffline() method call.

As for the cause of the issue, it stems from the way maven resolves dependencies from Arquillian in comparison to building. I had updated a library version, which now depends on the newer version of javassist. However, in considering all the other things within the pom.xml, maven brings it down to an earlier version when building.

However, the dependency resolution within the maven run through Arquillian considers a slightly different set of requirements and resolves to a later version of the lib which is not available.