diff --git a/test/fixtures/poro.rb b/test/fixtures/poro.rb
index a357c24e..2dd98642 100644
--- a/test/fixtures/poro.rb
+++ b/test/fixtures/poro.rb
@@ -38,6 +38,19 @@ end
 class WebLog < Model
 end
 
+class Mail < Model
+  def attachments
+    @attachments ||= [Image.new(url: 'U1'),
+                      Video.new(html: 'H1')]
+  end
+end
+
+class Image < Model
+end
+
+class Video < Model
+end
+
 ###
 ## Serializers
 ###
@@ -73,3 +86,17 @@ end
 class WebLogLowerCamelSerializer < WebLogSerializer
   format_keys :lower_camel
 end
+
+class MailSerializer < ActiveModel::Serializer
+  attributes :body
+
+  has_many :attachments, polymorphic: true
+end
+
+class ImageSerializer < ActiveModel::Serializer
+  attributes :url
+end
+
+class VideoSerializer < ActiveModel::Serializer
+  attributes :html
+end
diff --git a/test/unit/active_model/serializer/has_many_polymorphic_test.rb b/test/unit/active_model/serializer/has_many_polymorphic_test.rb
new file mode 100644
index 00000000..e5180cfe
--- /dev/null
+++ b/test/unit/active_model/serializer/has_many_polymorphic_test.rb
@@ -0,0 +1,189 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class HasManyPolymorphicTest < ActiveModel::TestCase
+      def setup
+        @association = MailSerializer._associations[:attachments]
+        @old_association = @association.dup
+
+        @mail = Mail.new({ body: 'Body 1' })
+        @mail_serializer = MailSerializer.new(@mail)
+      end
+
+      def teardown
+        MailSerializer._associations[:attachments] = @old_association
+      end
+
+      def model_name(object)
+        object.class.to_s.demodulize.underscore.to_sym
+      end
+
+      def test_associations_definition
+        assert_equal 1, MailSerializer._associations.length
+        assert_kind_of Association::HasMany, @association
+        assert_equal true, @association.polymorphic
+        assert_equal 'attachments', @association.name
+      end
+
+      def test_associations_embedding_ids_serialization_using_serializable_hash
+        @association.embed = :ids
+
+        assert_equal({
+          body: 'Body 1',
+          'attachment_ids' => @mail.attachments.map do |c|
+            { id: c.object_id, type: model_name(c) }
+          end
+        }, @mail_serializer.serializable_hash)
+      end
+
+      def test_associations_embedding_ids_serialization_using_as_json
+        @association.embed = :ids
+
+        assert_equal({
+          'mail' => {
+            :body => 'Body 1',
+            'attachment_ids' => @mail.attachments.map do |c|
+              { id: c.object_id, type: model_name(c) }
+            end
+          }
+        }, @mail_serializer.as_json)
+      end
+
+      def test_associations_embedding_ids_serialization_using_serializable_hash_and_key_from_options
+        @association.embed = :ids
+        @association.key = 'key'
+
+        assert_equal({
+          body: 'Body 1',
+          'key' => @mail.attachments.map do |c|
+            { id: c.object_id, type: model_name(c) }
+          end
+        }, @mail_serializer.serializable_hash)
+      end
+
+      def test_associations_embedding_objects_serialization_using_serializable_hash
+        @association.embed = :objects
+
+        assert_equal({
+          body: 'Body 1',
+          :attachments => [
+            { type: :image, image: { url: 'U1' }},
+            { type: :video, video: { html: 'H1' }}
+          ]
+        }, @mail_serializer.serializable_hash)
+      end
+
+      def test_associations_embedding_objects_serialization_using_as_json
+        @association.embed = :objects
+
+        assert_equal({
+          'mail' => {
+            body: 'Body 1',
+            attachments: [
+              { type: :image, image: { url: 'U1' }},
+              { type: :video, video: { html: 'H1' }}
+            ]
+          }
+        }, @mail_serializer.as_json)
+      end
+
+      def test_associations_embedding_nil_objects_serialization_using_as_json
+        @association.embed = :objects
+        @mail.instance_eval do
+          def attachments
+            [nil]
+          end
+        end
+
+        assert_equal({
+          'mail' => {
+            :body => 'Body 1',
+            :attachments => [nil]
+          }
+        }, @mail_serializer.as_json)
+      end
+
+      def test_associations_embedding_objects_serialization_using_serializable_hash_and_root_from_options
+        @association.embed = :objects
+        @association.embedded_key = 'root'
+
+        assert_equal({
+          body: 'Body 1',
+          'root' => [
+            { type: :image, image: { url: 'U1' }},
+            { type: :video, video: { html: 'H1' }}
+          ]
+        }, @mail_serializer.serializable_hash)
+      end
+
+      def test_associations_embedding_ids_including_objects_serialization_using_serializable_hash
+        @association.embed = :ids
+        @association.embed_in_root = true
+
+        assert_equal({
+          body: 'Body 1',
+          'attachment_ids' => @mail.attachments.map do |c|
+            { id: c.object_id, type: model_name(c) }
+          end
+        }, @mail_serializer.serializable_hash)
+      end
+
+      def test_associations_embedding_ids_including_objects_serialization_using_as_json
+        @association.embed = :ids
+        @association.embed_in_root = true
+
+        assert_equal({
+          'mail' => {
+            body: 'Body 1',
+            'attachment_ids' => @mail.attachments.map do |c|
+              { id: c.object_id, type: model_name(c) }
+            end,
+          },
+          attachments: [
+            { type: :image, image: { url: 'U1' }},
+            { type: :video, video: { html: 'H1' }}
+          ]
+        }, @mail_serializer.as_json)
+      end
+
+      def test_associations_embedding_nothing_including_objects_serialization_using_as_json
+        @association.embed = nil
+        @association.embed_in_root = true
+
+        assert_equal({
+          'mail' => { body: 'Body 1' },
+          attachments: [
+            { type: :image, image: { url: 'U1' }},
+            { type: :video, video: { html: 'H1' }}
+          ]
+        }, @mail_serializer.as_json)
+      end
+
+      def test_associations_using_a_given_serializer
+        @association.embed = :ids
+        @association.embed_in_root = true
+        @association.serializer_from_options = Class.new(ActiveModel::Serializer) do
+          def fake
+            'fake'
+          end
+
+          attributes :fake
+        end
+
+        assert_equal({
+          'mail' => {
+            body: 'Body 1',
+            'attachment_ids' => @mail.attachments.map do |c|
+              { id: c.object_id, type: model_name(c) }
+            end
+          },
+          attachments: [
+            { type: :image, image: { fake: 'fake' }},
+            { type: :video, video: { fake: 'fake' }}
+          ]
+        }, @mail_serializer.as_json)
+      end
+    end
+  end
+end