Minitest Spec for Rails.

test_helper.rb

require 'simplecov'
SimpleCov.start 'rails'

ENV["RAILS_ENV"] ||= "test"
require File.expand_path('../../config/environment', __FILE__)

require 'minitest/autorun'
require 'rails/test_help'
require 'factories'

# Doc-style test reporting (similar to --format=documentation in rspec) 
require 'turn'
# Available styles: :outline, :progress, :dotted, :pretty, :marshal, :cue
Turn.config.format = :outline
Turn.config.natural = true

# Reset the database for each test
require 'database_cleaner'
DatabaseCleaner.strategy = :transaction

class ActiveSupport::TestCase
  ActiveRecord::Migration.check_pending!
end

class Minitest::Spec
  include ActiveSupport::Testing::Assertions # assert_difference etc...
  include ActiveSupport::Testing::SetupAndTeardown # before, after

  # Support rspec-style context-blocks
  class << self
    alias_method :context, :describe
  end

  before { DatabaseCleaner.start }
  after { DatabaseCleaner.clean }

end

# A bit more dry validation tests
#     m = Message.create(text: '')
#     m.must_have_invalid :text
module Minitest::Assertions
  def assert_has_invalid(field, model)
    model.must_be :invalid?
    model.errors[field].must_be :present?
  end
end
ActiveRecord::Base.infect_an_assertion :assert_has_invalid, :must_have_invalid

# RSpec like `expect{}.to change` using this syntax:
#     -> { Message.create(text: 'A message') }.must_change 'Message.count', +1
class Proc
  infect_an_assertion :assert_difference, :must_change
  infect_an_assertion :assert_no_difference, :wont_change
end

# Make the controller methods (get, post etc...) work
class ControllerSpec < Minitest::Spec
  include Rails.application.routes.url_helpers
  include ActionController::TestCase::Behavior

  before do
    @routes = Rails.application.routes
  end
end
Minitest::Spec.register_spec_type(/Controller$/, ControllerSpec)

### Gemfile
group :test do
  gem 'minitest'
  gem 'minifacture'
  gem 'database_cleaner'
  gem 'capybara_minitest_spec'
  gem 'simplecov', require: false
  gem 'turn'
end

Manual configuration of Minitest for Rails, it uses the plain minitest gem so no need for minitest-rails or minitest-spec-rails - what you see is what you get.

It covers most of the things I missed from RSpec and is set up for both readable output and readable tests, but is still very minimal and quick.

I stole much of it from this gist: https://gist.github.com/sethbro/1784986