Ben Luther, a Flight Test Engineer at Gulfstream provides this definition of the Build-up Approach.
What is an incremental approach in flight test? I have defined it as being: The creation of cumulative sub-steps within a test program so as to slow the rate of change and/or limit the risk of a hazard, in the performance of a system under test. In a safety system context, this slower rate of change in system performance provides an opportunity to respond to test results and alter the conduct of testing if required to avoid adverse test outcomes.
[Luther, Ben. “In Defence of the Incremental Approach.” SETP Cockpit (July – December 2017): 38.]
Luther also presented at the 2016 Flight Test Safety Workshop.