An exemplary method and system for testing light-emitting diodes (LEDs) uses a camera module to take two bulb images of transparent bulbs connected to each of the LEDs. A first bulb image is captured when the LEDs are set in a power-on state, and a second bulb image is captured when the LEDs are set in a power-off state. The method divides each of the two bulb images into small pictures, and calculates an average pixel value of each of the small pictures. After calculating a first difference of each of the small pictures between the average pixel value and a first predetermined value, and a second difference of each of the small pictures between the average pixel value and a second predetermined value, the method ascertains a present state of each of the LEDs by comparing the two differences.