Covering normative statements via testcases

[OR13]

Test cases will cover normative statements, for example:

typ and cty values are easy to test, since they appear in header parameters.

However there are some tricky cases that require full verification... for example:

schema credentials and status credentials.

we'll need negative cases for those, and we might want to encode specific error messages, that some implementers might make use of and others might ignore.

Here are a few examples:

• Failed to verify credential status, could not dereference status list
• Failed to verify credential status, signature verification failed.
• Failed to verify credential status, could not dereference public key.
• Failed to verify credential status, status list no longer valid (expiration in the past)
• Failed to verify credential status, status list not yet valid (activation in the future)

I would like for use to encode some of these errors in test cases, even if a "pass" for the test case is simply raising a generic "error" flag.