invalid roles tests

[cookiecrook]

invalid roles tests like role="foo"

Should probably also have attribute parsing tests in here too. No telling what people or frameworks will insert:

• Various Unicode ranges, inc Emoji and zero space joiners.
• Whitespace.
• Punctuation.
• Escape chars. URL encoded chars, etc.

Don't rely solely on the assignAndVerifyRolesByRoleNames convenience method for this one, as passing those values through the JS context will likely bypass some of the parsing tests (escaped/encoded chars for example) that we'd want to verify whether it came from JS assignment or markup.

Also, escape characters and joiners shouldn't behave differently in markup or via JS assignment (el.role or el.setAttribute()) but it'd be worth testing all three types of role re-assignment.

Follow-on from #8

Update: See a subsection of these in wai-aria/role/fallback-roles.html.