test for json adapter

test/adapter/json/belongs_to_test.rb

@@ -0,0 +1,25 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class Adapter
+      class Json
+        class BelongsToTest < Minitest::Test
+          def setup
+            @post = Post.new(id: 42, title: 'New Post', body: 'Body')
+            @comment = Comment.new(id: 1, body: 'ZOMG A COMMENT')
+            @post.comments = [@comment]
+            @comment.post = @post
+
+            @serializer = CommentSerializer.new(@comment)
+            @adapter = ActiveModel::Serializer::Adapter::Json.new(@serializer)
+          end
+
+          def test_includes_post
+            assert_equal({id: 42, title: 'New Post', body: 'Body'}, @adapter.serializable_hash[:post])
+          end
+        end
+      end
+    end
+  end
+end