1. A computer-performed method of generating an executable and user-modifiable trace file script, the method comprising: first executing an executable instruction stream within a computer system that invokes a sequence of high-level procedures; and generating a trace file during execution of the executable instruction stream that represents invocations of the high-level procedure invocations as a human-readable script; and responsive to a subsequent command, second executing the trace file within the computer system to reproduce at least part of the behavior of the executable instruction stream.