A method tests at least three devices, each device including a test chain having a plurality of positions storing test data. The testing includes comparing test data in a last position of the test chain of each of the devices, and shifting test data in the test chains of each of the devices and storing a result of the comparison in a first position of the test chains of each of the devices. The comparing and the shifting and storing are repeated until all the stored test data has been compared. The at least three devices may have a same functionality and a same structure.