Remove vestigal `== 1`.
Improve spec a bit.
Use `channel` instead of `_channel`.
Remove unused attribute.
Fix typo.
Remove require.

This file was using a mutex but is no longer.
Rearrange helper methods.

- Put `redis_config` in the shared context that relies on it.
  This makes it clear why the YAML require was needed.
- Remove unused `redis_url`.