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Current [lib/debug.rb](https://docs.ruby-lang.org/en/3.0.0/DEBUGGER__.html) is no longer being maintained and it is not appropriate for current Ruby features. [Koichi Sasada](https://github.com/ko1) started writing new [lib/debug.rb](https://github.com/ruby/debug) (hereinafter referred to as the new debugger) to replace it(For more information, see [this article](https://dev.to/ko1/debug-gem-blog-initial-commit-3ip)). However, it was hard to write test for it because the test framework have to test the new debugger without interrupting debugger process. That's why we worked on developping the test framework for the new debugger as the part of GSoC 2021 project.