1. A method performed on at least one computer processor, said method comprising: receiving first tracer data observed from an application, said application comprising a plurality of inputs; identifying a plurality of sequences of said inputs; identifying a usage database comprising usage for each of said plurality of sequences from said first tracer data; receiving second tracer data observed from said application; identifying a subset of said plurality of sequences contained in said second tracer data; comparing said subset of said plurality of sequences to said usage frequency database to determine a coverage factor.