Add Testing

- [ ] http://erickt.github.io/blog/2015/09/22/if-you-use-unsafe/
- [x] https://github.com/Manishearth/rust-clippy

Start by reviewing the linked unsafe article and the rust-clippy repository, since these are the only investigation points in the issue. The issue does not name files, tests, or acceptance criteria, so the scope and definition of done need to be established before implementation.

索引モデルが issue の本文から書いたものです。