My point is simple: Only a FULL SCALE test can prove the reliability of such a system. Look at the "Patriot 1 Missile" It was a total failure. Why? Because it had never undergone a baptisim of fire.
The way complex defense systems are tested is determined largely by the defense contractors plus the DoD project managers. Both want the project to succeed and therefore create biased tests.
Explain to me how one could assure the proper functioning of something as complex as the Ballistic Missile Defense System without full-scale testing. I don't believe that it is remotely possible.