What is the typical procedure when determining antenna performance in an end product?

Ezurio (formerly Laird Connectivity) has an anechoic chamber with a 2-axis measuring the return loss of the antenna (ideally better than -9dBm) and to make EIRP (Equivalent Isotropically Radiated Power) pattern and TRP (Total Radiated Power). If the conducted power at the antenna feed is known, the peak and average antenna gains can be determined.