When trying to build coretests site, we can see ( https://jenkins.mw.lab.eng.bos.redhat.com/hudson/view/DevStudio/view/DevStudio_Trunk/job/jbosstools-3.3_trunk.coretests.aggregate/ ) that site cannot be built because it cannot resolve dependency from bundle org.jboss.tools.as.test.core to bundle org.jboss.ide.eclipse.as.doc.user .
Indeed, this org.jboss.ide.eclipse.as.doc.user bundle is not part of the AS update-site (that means it's not part of any of the feature published), so it it impossible for tests to resolve it while creating test site.
It is working fine in the AS job since the bundle is available in the reactor.

Fix is to add this org.jboss.ide.eclipse.as.doc.user bundle to a feature that is already published on as/site/category.xml .