Tool-based testing for composited systems

Tool-based testing of composited systems indirectly tests properties of a dynamic linked library for a desktop compositor such as DWMCore.dll via an algebraic structure of tools that define composition and rendering properties and derive equivalent resource models. The system tests for undesired side effects by examining characteristics of pixels from complicated render operations and employs a framework to test the composition and rendering of Desktop Windows Manager directly on the DWMCore.dll Application Programming Interface. The process includes mimicking uDWM.dll behavior by using resources with test patterns to take controlled measurements and validate primitives. The framework includes an infrastructure, a resource model, and tools. Each tool exposes a different composition or rendering property. A tool combinator exposes high level composition properties, including correct overlapping of transparent content and visual transformation (translation, scale, color transforms, etc.) by taking tools as input and using visual tree constructs to combine them.