Can't run unit test with "Execute FlexUnit Tests" in the FB4

Hi folks:

     I create some unit tests in my project,the test.swf execute correctly if I compile them and run it by ant.But once i ran every single file by "Execute FlexUnit Tests" in my IDE,I found them don't work...The window popped out,and the test function in the file didn't be invoked.

My workmates and I don't know why...Is there any one know something about it,Or get the same problem?

Thanks!