Method of operating an image sensor, image sensor performing the same, and electronic system including the same

An image sensor comprising:

• a pixel array configured to generate a plurality of analog pixel signals in response to incident light;
• a test pattern generator configured to generate a test pattern;
• and
• a plurality of column driving circuits configured to convert the plurality of analog pixel signals received from the pixel array into a first plurality of digital signals or to convert the test pattern into a second plurality of digital signals based on a selection signal,
• wherein the image sensor is configured to generate a test result pattern based on the second plurality of digital signals or image data based on the first plurality of digital signals, and
• wherein the image sensor is configured to convert the test pattern into the second plurality of digital signals using a first number of the plurality of column driving circuits in a first test mode and to convert the test pattern into the second plurality of digital signals using a second number of the plurality of column driving circuits in a second test mode.