A tester comprising a reference clock generating section for generating a reference clock having a first frequency, a first test rate generating section for generating a first test rate clock having a frequency which is about an integral multiple of the first frequency, a second test rate generating section for generating a second test rate clock having a frequency which is about an integral multiple of the first frequency and different from the frequency of the first test rate clock, a first driver section for supplying a test pattern to an electronic device according to the first test rate clock, and a second deriver section for supplying the test pattern to the electronic device according to the second test rate clock.