Well, this is just a shot in the dark, but I'm assuming that biometric testing would be the testing of biometric systems. So this could include reading a fingerprint, iris, facial recognition, blood sample! (joke) to gain access to a specific system.
Apart from that, you would need to verify, basically, anything a regular login test suite would include. If there are multiple levels of security, then you will probably need to test a user at each security level, ensure they can only gain access to the areas they are allowed to, etc.
Also, you should probably run testing for tolerance. Most of these systems use certain criteria to judge your authenticity. So a question I would raise would be, what is the tolerance for failure. If I cut my finger and have a scab on it, can I access the system? What about if I have bloodshot eyes? For facial recognition, what if I smile or frown? Am I able to "fake" my access? IE, can I lift a finger print and scan it a la James Bond? Depending on the level of security you are trying to protect, any of these can be taken into consideration.