Unit Tests and AttachFromFile

[kdsudac]

New unit test util's are really useful.

Ran into a little bit of a pain point with test.AttachFromFile(filename) since need to mock out open:

mo = mock.mock_open()

with mock.patch('openhtf.exe.phase_data.open', mo, create=True):
    phase_record = yield MyPhase

assert FILENAME in phase_record.attachments

Would be nice if we could make this happen under the hood.

[grybmadsci]

ah, good point, will definitely look into rolling this into the next round of updates to the unit test stuff :)