There should be better ways - hope anybody comment it

guard_exercism.md

Use guard-shell gem.

# terminal (at exercism/ruby/)
gem install guard guard-shell
guard init shell

# Guardfile
guard :shell do
  watch(/^(.+)\.rb$/) do |m|
    `ruby -I"lib:test" #{m[1].chomp('_test')}_test.rb`
  end
end

Use minitest-reporters gem to add Red and Green

# terminal
gem install minitest-reporters

# test_helper.rb
require "minitest/reporters"
Minitest::Reporters.use!

# Guardfile
guard :shell do
  watch(/^(.+)\.rb$/) do |m|
    `ruby -I"lib:test" -r"./test_helper" #{m[1].chomp('_test')}_test.rb`
  end
end

Add more options to Minitest::Reporters

# test_helper.rb
require "minitest/reporters"
reporter_options = {
  detailed_skip: false, # true by default
  fast_fail: true, # false by default
  color: true
}
Minitest::Reporters.use! [Minitest::Reporters::DefaultReporter.new(reporter_options)]

Run it

# terminal (at exercism/ruby/)
guard --notify false

Interesting. Is this contributing to exercism open source?

I'm wonder if we do all these directions within the ruby directory or the specific exercise directory ( for example in helloword directory)?

The answer is: in the exercism/ruby directory. Thank you @kkchu791 for asking, sorry for being late to answer! By the way, I just found your comment while I'm working on the listy-gisty, (do you remember this Study Group project?) which helps me go find old gists.