What DNA Test, through what company? Since he is a male, he carries the Y gene from his father, grandfather, great grandfather.....it is the only gene that passes through a male line basically with no change. You need to pick a company that has the largest Y gene databases and using "Surname Projects". He also needs to sign a form to allow them to match his Y results with any in their databases and that he can be contacted if a match is found. Now if a matched Y DNA surname is found and they also have signed an agreement to be contacted then the company will make contact possible. There may not be a match now but the DNA company will keep his results a long time and some male of his bio dads family....another son, brother, son of a brother, etc may get tested in the future.
DNA companies do not share DNA results, and may not even use the same testing methods for getting results. that I know of so if you have used a small company because they offered a sale then it will not be very helpful.