Some carefully crafted libraries make promises to their users beyond functionality and performance. Examples are: Fusion libraries promise intermediate data structures to be eliminated. Generic programming libraries promise that the generic implementation is identical to the hand-written one. Some libraries may promise allocation-free or branch-free code. Conventionally, the modus operandi in all these cases is that the library author manually inspects the (intermediate or final) code produced by the compiler. This is not only tedious, but makes it very likely that some change, either in the library itself or the surrounding eco-system, breaks the library’s promised without anyone noticing. This package provides a disciplined way of specifying such properties, and have them checked by the compiler. This way, this checking can be part of the ususal development cycle and regressions caught early. See the documentation in Test.Inspection or the project webpage for more examples and more information.