Use underscored json_root when serializing a collection

lib/active_model/serializer.rb

@@ -127,7 +127,7 @@ def initialize(object, options = {})
     end
 
     def json_key
-      @root || object.class.model_name.to_s.downcase
+      @root || object.class.model_name.to_s.underscore
     end
 
     def id

test/adapter/json/collection_test.rb

@@ -17,26 +17,27 @@ def setup
             @first_post.blog = @blog
             @second_post.blog = nil
 
-            @serializer = ArraySerializer.new([@first_post, @second_post])
-            @adapter = ActiveModel::Serializer::Adapter::Json.new(@serializer)
             ActionController::Base.cache_store.clear
           end
 
           def test_with_serializer_option
             @blog.special_attribute = "Special"
             @blog.articles = [@first_post, @second_post]
-            @serializer = ArraySerializer.new([@blog], serializer: CustomBlogSerializer)
-            @adapter = ActiveModel::Serializer::Adapter::Json.new(@serializer)
+            serializer = ArraySerializer.new([@blog], serializer: CustomBlogSerializer)
+            adapter = ActiveModel::Serializer::Adapter::Json.new(serializer)
 
             expected = {blogs:[{
               id: 1,
               special_attribute: "Special",
               articles: [{id: 1,title: "Hello!!", body: "Hello, world!!"}, {id: 2, title: "New Post", body: "Body"}]
             }]}
-            assert_equal expected, @adapter.serializable_hash
+            assert_equal expected, adapter.serializable_hash
           end
 
           def test_include_multiple_posts
+            serializer = ArraySerializer.new([@first_post, @second_post])
+            adapter = ActiveModel::Serializer::Adapter::Json.new(serializer)
+
             expected = { posts: [{
               title: "Hello!!",
               body: "Hello, world!!",
@@ -64,7 +65,15 @@ def test_include_multiple_posts
                 name: "Custom blog"
               }
             }]}
-            assert_equal expected, @adapter.serializable_hash
+            assert_equal expected, adapter.serializable_hash
+          end
+
+          def test_root_is_underscored
+            virtual_value = VirtualValue.new(id: 1)
+            serializer = ArraySerializer.new([virtual_value])
+            adapter = ActiveModel::Serializer::Adapter::Json.new(serializer)
+
+            assert_equal 1, adapter.serializable_hash[:virtual_values].length
           end
         end
       end

test/serializers/root_test.rb

@@ -5,13 +5,17 @@ class Serializer
     class RootTest < Minitest::Test
 
       def setup
-        @profile = Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })
-        @profile_serializer = ProfileSerializer.new(@post, {root: 'smth'})
+        @virtual_value = VirtualValue.new(id: 1)
       end
 
       def test_overwrite_root
-        setup
-        assert_equal('smth', @profile_serializer.json_key)
+        serializer = VirtualValueSerializer.new(@virtual_value, {root: 'smth'})
+        assert_equal('smth', serializer.json_key)
+      end
+
+      def test_underscore_in_root
+        serializer = VirtualValueSerializer.new(@virtual_value)
+        assert_equal('virtual_value', serializer.json_key)
       end
 
     end