A discipline that has proven unreliable.
Remember the "Patriot One" fiasco. Here was an "operational" system that did not work at all. This is what I fear for the missile shield. If it can not be a FULL-SCALE test, then it damn well better be a thorough test of as large a scale as practical. We probably SHOULD fire off all our ICBMs every ten or 20 years or so (at dummy targets), not at one time, but at the rate of 5% to 10% per year. This would keep the system in proper order and allow scheduled replacement of obsolete missiles.