updating tests to match new adapters structure

lib/active_model/serializer/adapter.rb

@@ -22,7 +22,8 @@ module ActiveModel
 
       def as_json(options = {})
         hash = serializable_hash(options)
-        include_meta(hash)
+        include_meta(hash) unless self.class == FlattenJson
+        hash
       end
 
       def self.create(resource, options = {})

lib/active_model/serializer/array_serializer.rb

@@ -7,8 +7,6 @@ module ActiveModel
       attr_reader :meta, :meta_key
 
       def initialize(objects, options = {})
-        options.merge!(root: nil)
-
         @objects = objects.map do |object|
           serializer_class = options.fetch(
             :serializer,
@@ -21,7 +19,7 @@ module ActiveModel
       end
 
       def json_key
-        @objects.first.json_key.pluralize if @objects.first
+        @objects.first.json_key if @objects.first
       end
 
       def root=(root)

lib/active_model/serializer/fieldset.rb

@@ -12,7 +12,7 @@ module ActiveModel
       end
 
       def fields_for(serializer)
-        key = serializer.json_key || serializer.class.root_name
+        key = serializer.json_key
         fields[key.to_sym]
       end