Apparatus having corresponding methods and computer-readable media comprises an input circuit to receive data over a communication channel, the data representing operation of a computer during an test interval and screen updates generated by the computer during the test interval; and a processor to generate a motion picture representing the test interval and contemporaneously comprising a stripchart area showing a first stripchart representing the operation of the computer based on the data, and a screen update area showing the screen updates represented by the second data stream; wherein the stripchart area and the screen update area are synchronized.