Just drop minitest.el. somewhere in your load-path. And:

(add-to-list 'load-path "~/emacs.d/vendor")
(require 'minitest)

The Spacemacs Ruby layer supports minitest-emacs as one of its configurable test runners. To set the default Ruby test runner to use this package, edit the ruby layer entry in the dotspacemacs-configuration-layers list defined in your .spacemacs file:

dotspacemacs-configuration-layers
'(
  (ruby :variables
        ruby-test-runner 'minitest)
)

See the Spacemacs Ruby layer documentation for more info.

M-x package-install minitest

To enable minitest mode on ruby files, simply add to your dotfile:

(add-hook 'ruby-mode-hook 'minitest-mode)

In case you are using Spacemacs, add the above line to dotspacemacs/user-config which is towards the end of your .spacemacs dotfile:

(defun dotspacemacs/user-config ()
	(add-hook 'ruby-mode-hook 'minitest-mode))

If you have another hook already in here make sure to add this hook within its own set of parenthesis so that there is only one hook per parenthesis.

If you are working on a Rails project, you can set minitest-use-rails to true in order to use the bin/rails test command when running examples.

You can run tests inside a Docker container by setting minitest-use-docker to true and minitest-docker-container to the name of the container. By default this will use the command docker-compose exec to run the minitest command, which assumes you already have the specified container running. To customize the command, edit the minitest-docker-command variable.

If you have yasnippet installed, you can load the snippets:

(eval-after-load 'minitest
  '(minitest-install-snippets))

The MIT License (MIT)

Copyright (c) 2013 Arthur Nogueira Neves

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.