1. A data processing method comprising: rendering a first image of a first user interface based on a first set of instructions; rendering a second image of a second user interface based on a second set of instructions; generating a first mask comprising a plurality of points, wherein each point in the first mask indicates whether a first point in the first image and a second point in the second image are different; rendering a third image of a third user interface based on a third set of instructions, wherein the first set of instructions are different than the third set of instructions and the first image is different than the third image; determining that the first image is equivalent to the third image based on the first image, the first mask, and the third image; wherein the method is performed by one or more computing devices.