Generally, when electronic hardware will be sold a certification requirement must be met, this certification is usually only required once unless changes are made to the hardware will affect the RF emission performance.
Once your design is working, some basic measurements are recommended to certification testing, FCC normally give some details on measuring digital radios.
Freescale provides an document for this basic measurements, a Pre-certification testing, those recommendations should be performed as part of design verification
-- Perform pre-certification testing or have the certification partner, perform the test to ensure passing before finalizing the design and formally submitting for certification --
http://cache.freescale.com/files/rf_if/doc/ref_manual/ZRFETRM.pdf
