A Minitest 5 plugin for running focused tests.
gem install minitest-line
ruby test/my_file -l 5
If you want to be able to run describe block by line number add
require 'minitest/line/describe_track'
This plugin was inspired by James Mead pull request to Minitest: Run a test by line number from the command line (a.k.a. "run focussed test")