So... Part 43 Appendix F says the 91.413 check on a transponder can be done with the unit on the test bench.
And, the 91.227 check can done during a 91.407(b) test flight IAW para H(1) above...
-but-
Of course, it's still not a "Preventive Maintenance" task as per FAR 43, Appendix A. So, you...