Implement has_one's and serialize_ids

test/fixtures/poro.rb

@@ -6,6 +6,14 @@ class Model
   def read_attribute_for_serialization(name)
     @attributes[name]
   end
+
+  def model
+    @model ||= Model.new(attr1: 'v1', attr2: 'v2')
+  end
+
+  def id
+    object_id
+  end
 end
 
 class ModelSerializer < ActiveModel::Serializer
@@ -20,3 +28,9 @@ class ModelSerializer < ActiveModel::Serializer
 
   attributes :attr1, :attr2
 end
+
+class AnotherSerializer < ActiveModel::Serializer
+  attributes :attr2, :attr3
+
+  has_one :model
+end

test/unit/active_model/serializer/has_one_test.rb

@@ -0,0 +1,35 @@
+require 'test_helper'
+require 'active_model/serializer'
+
+module ActiveModel
+  class Serializer
+    class HasOneTest < ActiveModel::TestCase
+      def setup
+        @model = ::Model.new({ :attr1 => 'value1', :attr2 => 'value2', :attr3 => 'value3' })
+        @model_serializer = AnotherSerializer.new(@model)
+      end
+
+      def test_associations_definition
+        associations = @model_serializer.class._associations
+
+        assert_equal 1, associations.length
+        assert_kind_of Association::HasOne, associations[0]
+        assert_equal 'model', associations[0].name
+      end
+
+      def test_associations_serialization_using_serializable_hash
+        @model_serializer.class._associations[0].embed = :ids
+        assert_equal({
+          'attr2' => 'value2', 'attr3' => 'value3', 'model_id' => @model.model.object_id
+        }, @model_serializer.serializable_hash)
+      end
+
+      def test_associations_serialization_using_as_json
+        @model_serializer.class._associations[0].embed = :ids
+        assert_equal({
+          'attr2' => 'value2', 'attr3' => 'value3', 'model_id' => @model.model.object_id
+        }, @model_serializer.as_json)
+      end
+    end
+  end
+end