Slide 13 of 15
We test that where conversion operations are done, they are done correctly. In particular, it is known that many are subject to rounding errors and such must be disclosed to the user. Failure of the test can arise from the lack of such disclosure rather than the occurrence of an error that is in fact unavoidable.
Be upfront rather than burying disclosure in an obscure technical document, e.g. correspondence to users (particularly that which invites upgrades) and external software packaging.