I should answer the first obvious question: yes, all dependencies are on the test classpath.
But, I have noticed other scenarios, like when attempting to deploy a mail-service.xml to the bootstrap at test-prep, that kick a similar error... even though the required types are totally available at build time.
Looks like a message you normally get when you are using incompatible library versions.
I'm going to have to write a guide on how to ask for help it seems.
If you get an exception you MUST provide the full stacktrace.