Perturbation analysis involves changing the data state at a location in an executing program and determining the effect of that change on the program's remaining computation. This technique has been used to estimate propagation rates during fault sensitivity analysis, and also to compare test sets and testing strategies. This paper describes an error flow model that allows emphasis to be placed on propagation analysis, which is implemented using data state perturbation. A perturbation-adequate testing strategy is defined that is similar in concept to mutation testing, and some results are presented that support the coupling effect and the consistency of perturbation-adequate testing. Some observations are made that relate mutation to perturbation.