1. A method of testing an image sensor having a plurality of sensing units, comprising: utilizing the image sensor to capture at least a dynamic scene to generate a plurality of sensing results corresponding to a plurality of captured images respectively, wherein each of the sensing results includes a plurality of sensing values generated by the sensing units respectively; and generating a testing result indicative of performance of the image sensor according to changing of the sensing results, wherein the test result records a number of defective sensing units each having a significant change ratio exceeds a threshold, and the significant change ratio of one sensing unit is a number of times that a significant change in the sensing values corresponding to successive captured images happens to a given number of the captured images, wherein the step of generating the testing result indicative of performance of the image sensor according to changing of the sensing results comprises: performing a pre-processing operation upon the sensing results to generating a plurality of processed sensing results, wherein each of the processed sensing results comprises a plurality of characteristic values corresponding to the sensing units respectively; and generating the testing result indicative of performance of the image sensor according to changing of the characteristic values, comprising: for each of the sensing units: calculating a changing ratio of a characteristic value corresponding to the sensing unit in the sensing results; and generating the testing result according to a number of sensing units each having a corresponding changing ratio falling within a specific interval, comprising: for each of the sensing units: calculating a difference between the changing ratio and a predetermined ratio to generate a ratio difference corresponding to the sensing unit; and calculating an absolute value of the ratio difference; and generating the testing result according to a number of sensing units each having a corresponding absolute value falling within a difference interval.