For example there is a Direct3D reference engine written in software so that all changes to DX9 and DX10 etc can be compared against the reference to check that its correct.
OpenGL has a set of conformance tests with known results - see 2.160 here
The cartoon read to me like this one after another page. Nothing they say is untrue but all the inferences were misleading or not true at all. Because google is using regression testing against reference renders of pages does not mean that MS, Apple or Mozilla is not.