when test-op'ed, we print the result object to *standard-output*. when used interactively, the test defun that was used to start the testing simply returns the result value which we inspect in slime when needed.
Do you see the same problems I see? I find that my test's output can get interleaved with irrelevant chaff. So some of our code has something like this:
i think we don't have such problems because in stefil tests are expanded into augmented defun's, so no compilation happens while the tests run (unless compilation at each run is requested for some tests, but that's very rare).
one exception is when the query compiler tests run in cl-perec. then we do get some interleaved compiler and test output, but the test output is only one char per test, so we don't mind so much...
what i do mind though, is that an (asdf:oos 'asdf:test-op :foo) does not return the result value of the test run, which could be inspected in slime.