move DefaultSerializer to a separate file, add tests

lib/active_model/default_serializer.rb

@@ -0,0 +1,18 @@
+module ActiveModel
+  # DefaultSerializer
+  #
+  # Provides a constant interface for all items, particularly
+  # for ArraySerializer.
+  class DefaultSerializer
+    attr_reader :object, :options
+
+    def initialize(object, options={})
+      @object, @options = object, options
+    end
+
+    def serializable_hash
+      @object.as_json(@options)
+    end
+  end
+
+end

lib/active_model/serializer.rb

@@ -457,19 +457,4 @@ def default_embed_options
     end
   end
 
-  # DefaultSerializer
-  #
-  # Provides a constant interface for all items, particularly
-  # for ArraySerializer.
-  class DefaultSerializer
-    attr_reader :object, :options
-
-    def initialize(object, options={})
-      @object, @options = object, options
-    end
-
-    def serializable_hash
-      @object.as_json(@options)
-    end
-  end
 end

lib/active_model_serializers.rb

@@ -3,6 +3,7 @@
 require "active_support/notifications"
 require "active_model"
 require "active_model/array_serializer"
+require "active_model/default_serializer"
 require "active_model/serializer"
 require "active_model/serializer/associations"
 require "set"

test/default_serializer_test.rb

@@ -0,0 +1,25 @@
+require "test_helper"
+require "test_fakes"
+
+class DefaultSerializerTest < ActiveModel::TestCase
+
+  def test_object_with_no_options
+    object = Model.new
+    serializer = ActiveModel::DefaultSerializer.new(object)
+    assert_equal object.as_json, serializer.serializable_hash
+  end
+
+  def test_object_with_options
+    object = Model.new
+    serializer = ActiveModel::DefaultSerializer.new(object, something: "hello")
+    assert_equal({something: "hello"}, serializer.options)
+    assert_equal object.as_json, serializer.serializable_hash
+  end
+
+  def test_array
+    array = [ {name: "Fred"} ]
+    serializer = ActiveModel::DefaultSerializer.new(array)
+    assert_equal array.as_json, serializer.serializable_hash
+  end
+
+end