A test pilot will be the first to fly a new, untested system. There are almost always surprises and problems that must be corrected. The flight tests are done in a very systematic, cautious, way so that every facet of prior test flights is understood before the next one is attempted. In fact, the first "flight" of a new airplane is usually just a high-speed taxi down the runway. Even on those tests, ugly surprises happen. A normal pilot of a commercial flight would not be expected to do anything experimental.In effect, this is the definition of a test pilot, they are going to take those risks (before the client or airline pilot has to), to show how a pilot interacts with those new systems and the changed aerodynamics of the craft.