Add more regression tests

I think it will be a good idea to include some regression test to this project to prevent performance degradations.
Are there any benchmarks people commonly use for testing the code?

No files, tests, benchmarks, or entry points are named. First identify the existing test and performance-measurement entry points, then confirm which commonly used benchmarks the project should adopt. Done means the benchmark set and regression-test scope are agreed and performance degradations can be detected.

Written by the indexing model from the issue text.