A method of testing analog and digital paths of a pixel in a row of an imager, includes the following steps: (a) injecting first and second charges into the analog path of the pixel, wherein the first charge is in response to a light exposure, and the second charge is in response to a built-in test; (b) sampling the first and second charges to form an image signal level and a test signal level, respectively; and (c) converting, by an analog-to-digital converter (ADC), the image signal level and the test signal level to form image data end test data, respectively. The method then validates the image data based on the test data.