Normal pr: Add problems

[![Code smell](https://www.pullreview.com/assets/code_smell-small.png)](https://www.pullreview.com/github/vanakenm/sandbox/reviews/feature/normal-pr) Use a logger instead of puts or add assertion.[ `Testing#new_method`](https://www.pullreview.com/github/vanakenm/sandbox/reviews/feature/normal-pr)