Flash Builder 4 does not seem to recognize unit tests

A colleague has an FB4 library project with unit tests.  When he tries to "Execute FlexUnit Tests" from the right-mouse-button menu, FB4 acts as if it's scanning the project for unit tests (a flickering dialog window pops up, as if it's scanning for tests), but it then claims that it couldn't find any UTs to run.

Has anyone else seen that behavior?