View source for NormativeButNotTestable

__NOTOC__
When writing a specificiation, it is sometimes tempting to use non-testable text for normative requirements; indeed, making sure a text is testable requires much more work than using simple text without caring about testability (see also [[TestableOrNot]]).

But using non testable text as normative requirements has many drawbacks:
* mandating something that cannot be tested is a no-op; how can you check whether something was indeed implemented if you cannot test it?
* non-testable requirements means that implementations are likely to differ on the said requirement, meaning that interoperability will be loose at best
* leaving a requirement in a fuzzy non testable state means leaving the disambiguation work to the implementors, making it much more costly and much more likely to generate confusion for the end users

See also [http://lists.w3.org/Archives/Public/www-qa/2005Dec/thread.html#msg1 a thread on www-qa].

http://www.w3.org/QA/images/qa.png 
[[Category:Qa]]