Nct problem help please ?

my car is due for nct soon but im worried its got the abs light on and i know nearly everyone gets failed for this yeah iv heard one or two still ped but most dont. The light came on a few months ago and would go off then stayed on . I brought it to the garage and they said i needed new brake pads and calipers so i got them , but it never went off after these were put on . I recently went back to the garage about it and they said we would have a look while we change your tires . When they were done i was told they couldnt see anything wrong with any of the braking equipment and didnt get anything when they used the probe to look for error codes. He told me go drive it for a few miles and it might go off .Sounded weird to me i took it to 3 other garages and none knew why it was showing a light all the time and one even said you might just have to try knocking it off till you do your test and hope for the best . I feel really annoyed i spent alot of money getting the car ready now im going to fail over something no one seems to be able to sort out .