A spare wheel is only checked if it is actually present. However there is no requirement for it as part of the NCT test itself. Nor is there a requirement for a mobility kit. I've put the 630i through twice with the non-run flats. I even put it through with German plates accidentally the last time, no issue.

Page 60 and 65 of the NCT manual cover off everything you need to know about spare wheel and NCT:

https://www.ncts.ie/NCT%20Manual%20Revise%20May%202012.pdf

Page 60 NOTES:
Examination is confined to tyres fitted to the road wheels. If, however, any defect on a tyre carried on a spare wheel is seen, the driver should be advised.

Page 65 NOTES:
1. Defects in a spare wheel tyre should not be considered a reason for failure.