### Question:
PlainMailboxManager implements MailboxManager { public void sessionControl( Object control, Object value ) throws Exception { session.sessionControl( control, value ); } PlainMailboxManager( TransportMessage transport, String uri,
		Resources resources );  PlainMailboxManager( TransportMessage transport, URL uri,
		Resources resources ); TransportMessage getTransport(); @Override String toString(); boolean sessionMessage( Who sender, Message msg ); void transportMessage( Who recipient, Message msg ); Mailbox transportCall( Who recipient, Message msg ); void register( Mailbox mb ); void unregister( Mailbox mb ); Mailbox getMailbox( Long msgid ); void redeliver( Who sender, Message msg ); int size(); Object sessionQuery( Object query ); void sessionControl( Object control, Object value ); void sessionNotify( Object event ); Object transportQuery( Object query ); void transportControl( Object control, Object value ); void transportNotify( Object event ); SessionMessage getSession(); void setSession( SessionMessage session );  }### Answer:
@Test public void sessionControl() throws Exception { Object CONTROL = "foo"; Object VALUE = "bar"; assertNull( session.what ); assertNull( session.control ); assertNull( session.value ); mmgr.sessionControl( CONTROL, VALUE ); assertSame( What.SESSION_CONTROL, session.what ); assertSame( CONTROL, session.control ); assertSame( VALUE, session.value ); }