We need to track compatibility with another implementation.

- By default try to use fixtures from another packs
- `remarked` / `marked` fixtures are preferable, because stmd data
  is partially outdated.
- If fixtures are missed or conflicting - create new ones here.

Rules:

1. Keep folders structure similar to [stmd](https://github.com/jgm/stmd) tests.
2. Don't forget to write case descriptions in fixtures.
3. Keep file name in lowercase, with underline for words separation.