How to measure a power amplifier

How to measure a power amplifier(PA) ? 

Here are two photos about how to measure the noise figure and gain roughly.

I used a Agilent E4448A PSA and a PA to do the noise calibration.

You can see two PAs on the same plane. The set-up is very fun because the DUT is another PA. Which one is the DUT??  guess ~ 

It is very difficult to measure the linearity (P1dB) especially high power type.

In my lab, we don't have such high power source.