require "test/unit"
require "test/unit/ui/console/testrunner"

# You can test whether an object is compliant with the ActiveModel API by
# calling ActiveModel::Lint.test(object). It will emit a Test::Unit
# output that tells you whether your object is fully compliant, or if not,
# which aspects of the API are not implemented.
#
# These tests do not attempt to determine the semantic correctness of the
# returned values. For instance, you could implement valid? to always
# return true, and the tests would pass. It is up to you to ensure that
# the values are semantically meaningful.
#
# Objects you pass in are expected to return a compliant object from a
# call to to_model. It is perfectly fine for to_model to return self.
module ActiveModel
  module Lint
    def self.test(object, verbosity = 2, output = STDOUT)
      test_class = Class.new(::Test::Unit::TestCase) do
        include Test

        define_method(:setup) do
          assert object.respond_to?(:to_model), "The object should respond_to :to_model"
          @object = object.to_model
          super
        end
      end

      ::Test::Unit::UI::Console::TestRunner.new(test_class, verbosity, output).start
    end

    module Test
      def assert_boolean(name, result)
        assert result == true || result == false, "#{name} should be a boolean"
      end

      # valid?
      # ------
      #
      # Returns a boolean that specifies whether the object is in a valid or invalid
      # state.
      def test_valid?
        assert @object.respond_to?(:valid?), "The model should respond to valid?"
        assert_boolean "valid?", @object.valid?
      end

      # new_record?
      # -----------
      #
      # Returns a boolean that specifies whether the object has been persisted yet.
      # This is used when calculating the URL for an object. If the object is
      # not persisted, a form for that object, for instance, will be POSTed to the
      # collection. If it is persisted, a form for the object will put PUTed to the
      # URL for the object.
      def test_new_record?
        assert @object.respond_to?(:new_record?), "The model should respond to new_record?"
        assert_boolean "new_record?", @object.new_record?
      end

      def test_destroyed?
        assert @object.respond_to?(:destroyed?), "The model should respond to destroyed?"
        assert_boolean "destroyed?", @object.destroyed?
      end

      # errors
      # ------
      #
      # Returns an object that has :[] and :full_messages defined on it. See below
      # for more details.
      def setup
        assert @object.respond_to?(:errors), "The model should respond to errors"
        @errors = @object.errors
      end

      # This module tests the #errors object
      module Errors
        # Returns an Array of Strings that are the errors for the attribute in
        # question. If localization is used, the Strings should be localized
        # for the current locale. If no error is present, this method should
        # return an empty Array.
        def test_errors_aref
          assert @errors[:hello].is_a?(Array), "errors#[] should return an Array"
        end

        # Returns an Array of all error messages for the object. Each message
        # should contain information about the field, if applicable.
        def test_errors_full_messages
          assert @errors.full_messages.is_a?(Array), "errors#full_messages should return an Array"
        end
      end

      include Errors
    end
  end
end