Simple answer is .. if the cat has been removed it won't pass..
one.. on emissions, and two.. on the fact that if a cat was fitted as original equipment it should be in place for the test..
unless you have a very friendly or blind MOT inspector.
if there is more than one cat fitted as OE then you may get away with removing one or more..
but no cat at all .. not a chance..
some people remove cats for performance purposes but always re fit them prior to the MOT test..
or driving the car on the public highway .. ahem
That's my take on it .. someone may know better..
I guess it may be possible to remove a DPF , fit a piece of plain pipe and then re-fit it prior to the MOT.. may need a re-map..
but as with a gasoline de-cat, and the new diesel regulations.. you're technically breaking the law.
How are they testing for soot . is it an emmisions test or just an eyeball to see the filter is in place ??