Grape formatter feature requested in #1258

- adds handling for when the returned resource is not serializable via ams
 - fix for when resource is an Array
 - Moves grape include to grape namespace. Changes Enumerable to Array because a plain hash is enumerable.
 - Add integration test
 - Refine scope of Grape version dependency
 - Assert that the response is equal to a manually defined JSON string
 - Add single module to include in Grape projects
 - Create a Serializable Resource to test rails-api from Grape
 - Update docs
 - Fix discrepency between ActiveRecord 4.0 - 4.1 and 4.2
 - Updated Changelog
 - Remove parens from `render`, use `serializable` in all tests.

test/grape_test.rb

@@ -0,0 +1,89 @@
+require 'test_helper'
+require 'grape'
+require 'grape/active_model_serializers'
+
+class ActiveModelSerializers::GrapeTest < Minitest::Test
+  include Rack::Test::Methods
+
+  class GrapeTest < Grape::API
+    format :json
+    include Grape::ActiveModelSerializers
+
+    resources :grape do
+      get '/render' do
+        render ARModels::Post.new(title: 'Dummy Title', body: 'Lorem Ipsum')
+      end
+
+      get '/render_with_json_api' do
+        post = ARModels::Post.new(title: 'Dummy Title', body: 'Lorem Ipsum')
+        render post, meta: { page: 1, total_pages: 2 }, adapter: :json_api
+      end
+
+      get '/render_array_with_json_api' do
+        post = ARModels::Post.create(title: 'Dummy Title', body: 'Lorem Ipsum')
+        post.dup.save
+        render ARModels::Post.all, adapter: :json_api
+      end
+    end
+  end
+
+  def app
+    GrapeTest.new
+  end
+
+  def test_formatter_returns_json
+    get '/grape/render'
+
+    post = ARModels::Post.new(title: 'Dummy Title', body: 'Lorem Ipsum')
+    serializable_resource = serializable(post)
+
+    assert last_response.ok?
+    assert_equal serializable_resource.to_json, last_response.body
+  end
+
+  def test_render_helper_passes_through_options_correctly
+    get '/grape/render_with_json_api'
+
+    post = ARModels::Post.new(title: 'Dummy Title', body: 'Lorem Ipsum')
+    serializable_resource = serializable(post, serializer: ARModels::PostSerializer, adapter: :json_api, meta: { page: 1, total_pages: 2 })
+
+    assert last_response.ok?
+    assert_equal serializable_resource.to_json, last_response.body
+  end
+
+  def test_formatter_handles_arrays
+    get '/grape/render_array_with_json_api'
+
+    expected = {
+      'data' => [
+        {
+          id: '1',
+          type: 'ar_models_posts',
+          attributes: {
+            title: 'Dummy Title',
+            body: 'Lorem Ipsum'
+          },
+          relationships: {
+            comments: { data: [] },
+            author: { data: nil }
+          }
+        },
+        {
+          id: '2',
+          type: 'ar_models_posts',
+          attributes: {
+            title: 'Dummy Title',
+            body: 'Lorem Ipsum'
+          },
+          relationships: {
+            comments: { data: [] },
+            author: { data: nil }
+          }
+        }
+      ]
+    }
+
+    assert last_response.ok?
+    assert_equal expected.to_json, last_response.body
+  end
+end