Abstract: A method for verifying a serializing function in a system including a plurality of processors and a test system including processors for verifying the serializing function. Each processor executes a verifying processing including the steps of: synchronizing an execution status of its own processor with an execution status of another processor; delaying an initiation of a next execution for a predetermined changeable period; issuing and executing a serializing instruction indicating a set of data read and write processings; and verifying whether the serializing instruction is normally executed or not. By controlling a timing of the execution of the serializing instruction at random between each processor, it is possible to verify normality of the serializing function satisfactorily and in a short time, while specifying whether cause for a fault occurring in the entire system is due to the serializing function or not.