The build-up approach is the fundamental safety principle in flight test.
Build up from the safest conditions: start from the middle of the envelope in airspeed, altitude, weight & cg.
Build-up approach: Take smaller steps as you get closer to risky conditions or the edge of the envelope.
The build-up approach is not formally defined anywhere but is widely used and well understood in principle.
Though it is not clearly defined, there are 5 build-up approach examples in the Introduction to Flight Test Engineering – AGARD Flight Test Techniques Series.