It seemed inadvisable to me to fly a brand new A/C into IFR conditions. I assume this wasn't it's first flight but still I think until it has a few hours on it one should stay VFR and near the field, just in case. I think it is always advisable to stay close to the base and VFR when test flying an A/C after major work has been done; brand new, overahauls, major repairs, and of course annual inspections.