http://java.net/jira/browse/MACOSX_PORT-683 submitted 2011/11/10 by Yuri Nesterenko
In this test Robot does press mouse button then Control key, drags, releases Control key then moves back to the target and releases the mouse button. Apparently drag termination occurs upon a Control release. (Note the resulting dropedData, it is a concatenation of 2 strings). That is wrong, termination is due on mouse release only.
Additionally, if you start working on this test, try to run it several times in row: sometimes it fails for a different reason, and I suspect it is not a test problem, either.