1. A post-silicon validation method for debugging a semiconductor device with one or more observable connections, the method comprising: testing, by one or more processors, the semiconductor device over a plurality of time intervals, wherein the testing is associated with an expected test outcome and causes the semiconductor device to produce an actual output and one or more signals, wherein each signal is associated with an observable connection; logging, by one or more processors, a group of signatures for the signals; dividing, by one or more processors, the group of signatures into a passing group having passing group signature values if the actual output conforms with the expected test outcome or a failing group having failing group signature values if the actual output does not conform with the expected test outcome; determining, by one or more processors, a model of signal behavior for each of the one or more signals by (i) calculating a passing group mean signature value from each of the passing group signature values tested during the same time interval to form a passing group band centered about the mean passing group signature values over each of the plurality of time intervals and bounded by a threshold passing range, and (ii) calculating a failing group mean signature value from each of the failing group signature values tested during the same time interval to form a failing group band centered about the mean failing group signature values over each of the plurality of time intervals and bounded by a threshold failing range; and identifying, by one or more processors, (i) the signals associated with a divergence of the failing group band from the passing group band, wherein the divergence occurs when any portion of the failing group band threshold failing range is no longer within the threshold passing range, and (ii) a time interval from among the plurality of time intervals associated with the divergence.