1. A system for validating output of a composited system in a test suite, the system comprising: one or more processing devices; a memory; and one or more modules stored on the memory and executable by the one or more processing devices to: communicate with a shared library for a desktop compositor directly by forming a dedicated channel with the shared library and creating a render target after the dedicated channel is formed; render primitives by adding nodes to a visual tree, where the created render target acts as a root of the visual tree; generate a graphics oracle to predict a rendering; and compare composition or rendering primitives against the graphics oracle based on at least a portion of the visual tree; and output error information if the comparison produces a result greater than a threshold of human perception.