EnterpriseArchiveImpl extends EnterpriseContainerBase which extends ContainerBase which implements ClassContainer.

However addClass from ClassContainer interface throws UnsupportedOperationException.

This is not nice. MockContexts extension for Arquillian does this:

if (appArchive instanceof ClassContainer) {
            ((ClassContainer) appArchive).addClass(MockViewScopedContext.class);
            ((ClassContainer) appArchive).addClass(MockConversationScopedContext.class);
        }

To avoid such problems, and for EAR it hits UnsupportedOperationException. Very not nice.