Add key option to serializer associations

test/adapter/json_api/json_api_test.rb

@@ -0,0 +1,38 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class Adapter
+      class JsonApiTest < Minitest::Test
+        def setup
+          ActionController::Base.cache_store.clear
+          @author = Author.new(id: 1, name: 'Steve K.')
+          @post = Post.new(id: 1, title: 'New Post', body: 'Body')
+          @first_comment = Comment.new(id: 1, body: 'ZOMG A COMMENT')
+          @second_comment = Comment.new(id: 2, body: 'ZOMG ANOTHER COMMENT')
+          @post.comments = [@first_comment, @second_comment]
+          @first_comment.post = @post
+          @second_comment.post = @post
+          @post.author = @author
+          @blog = Blog.new(id: 1, name: "My Blog!!")
+          @post.blog = @blog
+
+        end
+
+        def test_custom_keys
+          serializer = PostWithCustomKeysSerializer.new(@post)
+          adapter = ActiveModel::Serializer::Adapter::JsonApi.new(serializer)
+
+          assert_equal({
+            reviews: { data: [
+                        {type: "comments", id: "1"},
+                        {type: "comments", id: "2"}
+                    ]},
+            writer: { data: {type: "authors", id: "1"} },
+            site: { data: {type: "blogs", id: "1" } }
+            }, adapter.serializable_hash[:data][:relationships])
+        end
+      end
+    end
+  end
+end