Rename ArraySerializer to CollectionSerializer for clarity

test/serializers/configuration_test.rb

@@ -3,8 +3,25 @@ require 'test_helper'
 module ActiveModel
   class Serializer
     class ConfigurationTest < Minitest::Test
+      def test_collection_serializer
+        assert_equal ActiveModel::Serializer::CollectionSerializer, ActiveModel::Serializer.config.collection_serializer
+      end
+
       def test_array_serializer
-        assert_equal ActiveModel::Serializer::ArraySerializer, ActiveModel::Serializer.config.array_serializer
+        assert_equal ActiveModel::Serializer::CollectionSerializer, ActiveModel::Serializer.config.array_serializer
+      end
+
+      def test_setting_array_serializer_sets_collection_serializer
+        config = ActiveModel::Serializer.config
+        old_config = config.dup
+        begin
+          assert_equal ActiveModel::Serializer::CollectionSerializer, config.collection_serializer
+          config.array_serializer = :foo
+          assert_equal config.array_serializer, :foo
+          assert_equal config.collection_serializer, :foo
+        ensure
+          ActiveModel::Serializer.config.replace(old_config)
+        end
       end
 
       def test_default_adapter