Methods and apparatus for dynamically (AC) testing a target circuit within a main circuit include: providing respective sets of input latches from among a plurality of latches of the main circuit; reconfiguring connections of at least some of the input latches from normal connections within the main circuit such that each set of input latches is connected in series and directs an input bit stream from an associated source node into an associated input node of the target circuit; scanning a plurality of sets of input bits into the respective sets of input latches such that each latch of each set of input latches contains a respective bit of an associated one of the sets of input bits; and scanning each of the sets of input bits serially into the respective input nodes of the target circuit at a sufficiently high frequency to dynamically test the target circuit.