This does work as is, but a class is not necessary here. Also, tthere are some subtle pitfalls that one can fall into if you're not careful using classes in `py.test`, so generally I think it's better to *not* use a test class unless you have some particular reason.  `py.test` will always run test functions that are named ``test_*``, so just remove the class and unindent the function.  You might also rename the function to just ``test_make_kernel``, seeing as how it doesn't just use airy.