Airport MoTs
Non precision approaches in EU are tested to 100 feet below system minima eg: NDB, VOR, SRAs
ILS CAT 3 has Roll Out Guidance check for auto-land which is flown at 50 feet manually (180KIAS gear up in Multi crewed B200/350s) as there are no Calibration aircraft with an A/P that will respond accurately enough.
ILS signal in space is checked both above and below glide path, as well as left and right of localiser based centreline.
Cobham and Aerodata GmbH use a Flight Inspection system that utilises a ground based laser- this requires suitable MET visibility to lock onto the aircraft's reflector - it gives extremely good accuracy and acts as a datum line for the ILS calibration.
They also test and assist with the system design of SIDS/STARS/PARs/MLS/ and GPS based approaches.
Post Accident: I recall LHR was tested after the BA B777 glider incident.