If you've spent 2 years amassing 2000 real world sample inputs, I think this is a very valid way of going that extra bit further to test your system. Of course

If you've spent 2 years amassing 2000 real world sample inputs, I think this is a very valid way of going that extra bit further to test your system. Of course it's not possible to capture every possible test case when generating random input but using Markov chains seems like a good way to get 'sensible' data out of a random process. It is likely they exposed bugs in their parser that they would never have found by loading in real world make files.