Spot on. Can't think of any test but in my case I had some warning as it was difficult to lock and unlock so I had a look and so lucky that door was open when it eventually could not be unlocked when the "latch" was in closed position. There is a small sliding bit under the latch which would not move to allow it to unlock. I could move it with a small screw driver while door was open but obviously it would be impossible when door was closed. No amount of juggling the connecting rods from door latches helped so I presume something internal in mechanism broke.

