diff --git a/lib/active_model/serializer/adapter/json.rb b/lib/active_model/serializer/adapter/json.rb
index 68dba220..970de04b 100644
--- a/lib/active_model/serializer/adapter/json.rb
+++ b/lib/active_model/serializer/adapter/json.rb
@@ -3,9 +3,16 @@ module ActiveModel
     class Adapter
       class Json < Adapter
         def serializable_hash(options = {})
-          serializer.attributes.each_with_object({}) do |(attr, value), h|
-            h[attr] = value
+          @hash = serializer.attributes
+
+          serializer.associations.each do |name, association|
+            if association.respond_to?(:each)
+              @hash[name] = association.map(&:attributes)
+            else
+              @hash[name] = association.attributes
+            end
           end
+          @hash
         end
       end
     end
diff --git a/test/adapter/json/belongs_to_test.rb b/test/adapter/json/belongs_to_test.rb
new file mode 100644
index 00000000..498f1d98
--- /dev/null
+++ b/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
diff --git a/test/adapter/json/has_many_test.rb b/test/adapter/json/has_many_test.rb
new file mode 100644
index 00000000..d1534e6b
--- /dev/null
+++ b/test/adapter/json/has_many_test.rb
@@ -0,0 +1,31 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class Adapter
+      class Json
+        class HasManyTestTest < Minitest::Test
+          def setup
+            @post = Post.new(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
+
+            @serializer = PostSerializer.new(@post)
+            @adapter = ActiveModel::Serializer::Adapter::Json.new(@serializer)
+          end
+
+          def test_has_many
+            assert_equal([
+                           {id: 1, body: 'ZOMG A COMMENT'},
+                           {id: 2, body: 'ZOMG ANOTHER COMMENT'}
+                         ], @adapter.serializable_hash[:comments])
+          end
+        end
+      end
+    end
+  end
+end
+
diff --git a/test/adapter/json_api/has_many.rb b/test/adapter/json_api/has_many.rb
index ad8c3c2f..435079d7 100644
--- a/test/adapter/json_api/has_many.rb
+++ b/test/adapter/json_api/has_many.rb
@@ -14,7 +14,7 @@ module ActiveModel
             @second_comment.post = @post
 
             @serializer = PostSerializer.new(@post)
-            @adapter = ActiveModel::Serializer::Adapter::JsonApiAdapter.new(@serializer)
+            @adapter = ActiveModel::Serializer::Adapter::JsonApi.new(@serializer)
           end
 
           def test_includes_comment_ids
diff --git a/test/adapter/json_test.rb b/test/adapter/json_test.rb
index f8e753da..1d2e35a6 100644
--- a/test/adapter/json_test.rb
+++ b/test/adapter/json_test.rb
@@ -3,23 +3,24 @@ require 'test_helper'
 module ActiveModel
   class Serializer
     class Adapter
-      class JsonAdapterTest < Minitest::Test
+      class JsonTest < Minitest::Test
         def setup
-          @profile = Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })
-          @profile_serializer = ProfileSerializer.new(@profile)
+          @post = Post.new(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
 
-          @adapter = Json.new(@profile_serializer)
+          @serializer = PostSerializer.new(@post)
+          @adapter = ActiveModel::Serializer::Adapter::Json.new(@serializer)
         end
 
-        def test_serializable_hash
-          assert_equal({name: 'Name 1', description: 'Description 1'}, @adapter.serializable_hash)
-        end
-
-        def test_simple_adapter
-          assert_equal('{"name":"Name 1","description":"Description 1"}',
-                       @adapter.to_json)
-
-JSON
+        def test_has_many
+          assert_equal([
+                         {id: 1, body: 'ZOMG A COMMENT'},
+                         {id: 2, body: 'ZOMG ANOTHER COMMENT'}
+                       ], @adapter.serializable_hash[:comments])
         end
       end
     end