Michael Hartl uses the minitest-reporters gem to colorize test results in the third edition of the excellent Ruby on Rails Tutorail. I prefer minitest-rg. To use it instead:

  1. Remove (or just don't add) these lines to test/test_helper.rb:

    require 'minitest/reporters'
    Minitest::Reporters.use!
  2. Replace this section of the Gemfile:

    group :test do
      gem 'minitest-reporters', '1.0.5'
      gem 'mini_backtrace',     '0.1.3'
      gem 'guard-minitest',     '2.3.1'
    end

    With this:
    group :test do
      gem 'minitest',           '5.7.0'
      gem 'mini_backtrace',     '0.1.3'
      gem 'guard-minitest',     '2.3.1'
      gem 'minitest-rg',        '5.1.0'
    end
    The order is important. Calling minitest-rg earlier causes problems.