A new test is now passing and so we can remove it from the failure
whitelist.

Add note about JSON tests maybe being wrong.

- Add note about the JSON test maybe not being correct yet.
- Add test to checks the generated names for double underscores to be sure they
  are what is expected.

- String behaviors
- Testing only valid JSON is allowed

Add more JSON tests around underscores

The failure lists were falling out of date because the
tests would pass even if people forgot to remove failures
from the list.