Königsberg - Ruby
I started solving problem with Ruby because it was one of the first languages I learned and took seriously. If you're interested in learning Ruby as well, I highly recommend reading David A. Black's The Well-Grounded Rubyist since it will give you the tools you need to tackle problems.
You can run specific sets of problems like this:
$ rake test:advent
If you want to run a specific test, try
$ rake test:advent TEST=test/advent/2017/year2017day1_test
The workflow for adding new problems is to use TDD with a simplified version of
the problem and a nil placeholder for the site-verifiable version. After using
the Project Euler website to verify (or if the problem was already solved in a
different language) this placeholder can be replaced with a real test.