I also did not get the "on the fly" syntax working, not even in the console but I think that was a JDK version issue for me.

I assume you're using H2 in-memory so just put the "procedure class" right in your src/test/java and will be on the classpath. If you running the H2 in server mode and connecting via TCP, then you would need to include your classes directory on the H2 classpath.

Note: I left package names off of my H2StoredProcedures class for brevity.