minitest + shoulda-matchers

post_test.rb

gem "minitest"
require "minitest/spec"
require "minitest/autorun"
require "active_model"
require "turn"
require "shoulda-matchers"

class MiniTest::Unit::TestCase
  include Shoulda::Matchers::ActiveModel
  extend Shoulda::Matchers::ActiveModel
end

class Post
  attr_accessor :title

  include ActiveModel::Validations
  validates :title, :presence => true, :length => 2..16
end

class MiniTest::Spec
  class << self
    def it_must &block
      matcher = yield

      it "must #{matcher.description}" do
        result = matcher.matches? subject
        assert result, matcher.failure_message
      end
    end

    def it_wont &block
      matcher = yield

      it "wont #{matcher.description}" do
        result = matcher.does_not_match? subject
        assert result, matcher.negative_failure_message
      end
    end
  end
end

describe "Post" do
  subject { Post.new }

  it_must { ensure_length_of(:title).is_at_least(2).is_at_most(16) }
end