ActiveModel::Lint for RSpec without loading Rails

active_model_lint.rb

# hijacked from :http://library.edgecase.com/activemodel-lint-test-for-rspeca
#
# Usage:
#
# describe SomeModelClass do
#   it_should_behave_like "ActiveModel" do
#     let(:model) { SomeModelClass.new }
#   end
# end

shared_examples_for "ActiveModel" do
  require 'test/unit/assertions'
  require 'active_model/lint'
  require 'active_support/core_ext/object/blank'

  include Test::Unit::Assertions
  include ActiveModel::Lint::Tests

  # to_s is to support ruby-1.9
  ActiveModel::Lint::Tests.public_instance_methods.map(&:to_s).grep(/^test/).each do |method|
    example method.gsub('_',' ') do
      send method
    end
  end
end

plain_ruby_object_model_spec.rb

require 'support/active_model_lint'
require 'plain_ruby_object_model'

describe PlainRubyObjectModel do
  it_should_behave_like "ActiveModel" do
    let(:model) { PlainRubyObject.new }
  end
end

some_model.rb

class PlainRubyObject
  include ActiveModel::Conversion
  extend ActiveModel::Naming

  def to_model
    self
  end

  def persisted?
    false
  end

  def valid?
    true
  end

  def errors
    obj = Object.new
    def obj.[](key)         [] end
    def obj.full_messages() [] end
    obj
  end
end