This didn't happen at an airline, or in an Airbus, but it still relates. Started a trip on an airplane that had maint done overnight that involved running the APU. During preflight checks the APU fire test failed. Called maint and turns out the tech had only recently left so he came back out in just a few mins. Upon talking to him and mentioning the fire test he commented that they (mx) never do the fire test before starting the engines/apu. So just because something is supposed to be done does not mean it will be!