Make test attributes explicit

- Organize test poros with associations and by serializer
- Freeze derived attributes/associations against mutation
- Cleanup PORO fixtures

lib/active_model_serializers.rb

@@ -38,6 +38,14 @@ module ActiveModelSerializers
     @default_include_directive ||= JSONAPI::IncludeDirective.new(config.default_includes, allow_wildcard: true)
   end
 
+  def self.silence_warnings
+    original_verbose = $VERBOSE
+    $VERBOSE = nil
+    yield
+  ensure
+    $VERBOSE = original_verbose
+  end
+
   require 'active_model/serializer/version'
   require 'active_model/serializer'
   require 'active_model/serializable_resource'

lib/active_model_serializers/model.rb

@@ -3,42 +3,58 @@
 # serializable non-activerecord objects.
 module ActiveModelSerializers
   class Model
-    include ActiveModel::Model
     include ActiveModel::Serializers::JSON
+    include ActiveModel::Model
+
+    class_attribute :attribute_names
+    # Initialize +attribute_names+ for all subclasses.  The array is usually
+    # mutated in the +attributes+ method, but can be set directly, as well.
+    self.attribute_names = []
 
     def self.attributes(*names)
-      attr_accessor(*names)
+      self.attribute_names |= names.map(&:to_sym)
+      # Silence redefinition of methods warnings
+      ActiveModelSerializers.silence_warnings do
+        attr_accessor(*names)
+      end
     end
 
-    attr_reader :attributes, :errors
+    attr_reader :errors
+    # NOTE that +updated_at+ isn't included in +attribute_names+,
+    # which means it won't show up in +attributes+ unless a subclass has
+    # either <tt>attributes :updated_at</tt> which will redefine the methods
+    # or <tt>attribute_names << :updated_at</tt>.
+    attr_writer :updated_at
+    # NOTE that +id+ will always be in +attributes+.
+    attributes :id
 
     def initialize(attributes = {})
-      @attributes = attributes && attributes.symbolize_keys
       @errors = ActiveModel::Errors.new(self)
       super
     end
 
-    # Defaults to the downcased model name.
-    def id
-      attributes.fetch(:id) { self.class.name.downcase }
+    # The the fields in +attribute_names+ determines the returned hash.
+    # +attributes+ are returned frozen to prevent any expectations that mutation affects
+    # the actual values in the model.
+    def attributes
+      attribute_names.each_with_object({}) do |attribute_name, result|
+        result[attribute_name] = public_send(attribute_name).freeze
+      end.with_indifferent_access.freeze
     end
 
-    # Defaults to the downcased model name and updated_at
+    # To customize model behavior, this method must be redefined. However,
+    # there are other ways of setting the +cache_key+ a serializer uses.
     def cache_key
-      attributes.fetch(:cache_key) { "#{self.class.name.downcase}/#{id}-#{updated_at.strftime('%Y%m%d%H%M%S%9N')}" }
+      ActiveSupport::Cache.expand_cache_key([
+        self.class.model_name.name.downcase,
+        "#{id}-#{updated_at.strftime('%Y%m%d%H%M%S%9N')}"
+      ].compact)
     end
 
-    # Defaults to the time the serializer file was modified.
+    # When no set, defaults to the time the file was modified.
+    # See NOTE by attr_writer :updated_at
     def updated_at
-      attributes.fetch(:updated_at) { File.mtime(__FILE__) }
-    end
-
-    def read_attribute_for_serialization(key)
-      if key == :id || key == 'id'
-        attributes.fetch(key) { id }
-      else
-        attributes[key]
-      end
+      defined?(@updated_at) ? @updated_at : File.mtime(__FILE__)
     end
 
     # The following methods are needed to be minimally implemented for ActiveModel::Errors