Allow tests te be failed ?

We say that a test with f is expected to be failed, and we are thinking on #20 (closed).

But sometimes we would like to allow a test to fail. It's not expected, but under some circonstances, it may fail. In this case, we do not want to label f if #20 (closed) is resolved, we do not want to break a dev-ci pipeline... (but the user may want to be informed, it could be displayed at the end of the pipeline, like the current situation for TODO-but-ok before #20 (closed).)

Do we need a new letter for these tests ?