It would be nice if there was a command-line option to tell the test runner to call gc.collect() after each test.

See https://groups.google.com/d/msg/python-tulip/tstjvOQowIU/IRihc8NCHZUJ -- Glyph points out that always doing this is problematic because it slows down tests too much; OTOH it's a useful option to have in case you're tracking down something that happens (or doesn't happen) when an object is collected (e.g. in __del__).