I was really sure that 'python_d -m test' worked a week ago, in the sense that test_idle was run without incident in its proper alphabetical sequence,  before I said so and uploaded the patch. Now, there are (different) error messages with both 'python_d -m test' and 'python_d -m test test_idle'. (I did not try the latter before, only 'python_d -m test.test_idle', with the added '.' whose importance I now understand.) One of the two error messages includes what David reported. When I can, will report the other, and also will try to 'hg update' to a week ago to reproduce the remembered success. If I cannot, I will try options to determine the boundaries of the bug in the interacton between unittest and regrtest and a decent workaround that avoids duplicating code while running under both unittest and regrtest.

I sent Todd the Windows files to examine, modify, and test.

(Nick: neither unittest nor regrtest can run tests hidden within patches on the tracker. However, the point is currently moot for this issue. It might someday be a python-dev or python-ideas post.)