Email on success after build failure

On a failing test you get an email (sensible) but you don't get an email on a successful test (sensible). The problem is that after a failing test if someone pushes a fix then you don't get notified.

Essentially I would like a 'success' email added, but only if the previous test was a failure. At the moment you have to manually log in to check if someone pushed a working test after the failing one to know that it's been fixed.