In http://anonsvn.jboss.org/repos/jbosstools/trunk/as/tests/org.jboss.ide.eclipse.as.archives.integration.test/,

build.properties defines that this plugin will have a nested jar in it:

jars.compile.order = jbossasarchivesintegrationtest.jar
output.jbossasarchivesintegrationtest.jar = bin/

however, MANIFEST.MF points its classpath definition at the root, assuming there'll be a classes/*.class folder, not a rooted jar:

Bundle-ClassPath: .

You can't have it both ways – suggest replacing "jbossasarchivesintegrationtest.jar" with "." in build.properties.