The article shows that a software system that is in the process of testing can be considered as a non-equilibrium system in the transient mode. The simulation of this transitional process was carried out using an electric equivalent circuit. Modeling allowed to conclude that in the process of testing real and ideal systems that interact with each other. The report draws an analogy between the process of identifying defects in a program and the transition process in an equivalent electrical circuit. This made it possible to explain some of the features of the defect detection process.