Add dependency cycle detection/handling.  Some tests that could be run will not be run; to detect those tests that are actually actively participating in the cycle will require decomposing the dependency graph into its strongly-connected components--something I can do, but given how hard it is to actually establish a cycle in the first place, I don't see it as valuable to add.  This could change if we begin allowing pre-declaration of tests, but I think that unlikely.
Add dependency cycle detection/handling.  Some tests that could be
run will not be run; to detect those tests that are actually actively
participating in the cycle will require decomposing the dependency
graph into its strongly-connected components--something I can do, but
given how hard it is to actually establish a cycle in the first
place, I don't see it as valuable to add.  This could change if we
begin allowing pre-declaration of tests, but I think that unlikely.

klmitch/dtest,klmitch/dtest