If this test has a specific purpose it will probably only act on a specific file that is tailored for that purpose.  I'm not sure I see a need for this in the argument list.  Moreover, it could incorrectly suggest that this test should act on multiple files.

Now, if the test is designed for (or later refactored for) acting on multiple files, then I agree.  Otherwise, I think it is better to leave it hard coded.

P.S. what do other tests do in MOAB?