A testing method includes following steps. An electronic image is captured by an electronic device. A test device detect whether the image has any black bar. If the image has a black bar, pixel values in the black bar are extracted. If the pixel values in the black bar are all the same, a test result of imaging software error is presented. If the pixel values in the black bar are different from each other, a test result of mechanism error is presented. A test system associated with the testing method is also disclosed.