Make test attributes explicit

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

test/serializers/associations_test.rb

@@ -8,7 +8,7 @@ module ActiveModel
         @author.roles = []
         @blog = Blog.new(name: 'AMS Blog')
         @post = Post.new(title: 'New Post', body: 'Body')
-        @tag = Tag.new(name: '#hashtagged')
+        @tag = Tag.new(id: 'tagid', name: '#hashtagged')
         @comment = Comment.new(id: 1, body: 'ZOMG A COMMENT')
         @post.comments = [@comment]
         @post.tags = [@tag]
@@ -53,7 +53,7 @@ module ActiveModel
 
           assert_equal :tags, key
           assert_nil serializer
-          assert_equal [{ name: '#hashtagged' }].to_json, options[:virtual_value].to_json
+          assert_equal [{ id: 'tagid', name: '#hashtagged' }].to_json, options[:virtual_value].to_json
         end
       end
 
@@ -62,7 +62,13 @@ module ActiveModel
                       .associations
                       .detect { |assoc| assoc.key == :comments }
 
-        assert association.serializer.first.custom_options[:custom_options]
+        comment_serializer = association.serializer.first
+        class << comment_serializer
+          def custom_options
+            instance_options
+          end
+        end
+        assert comment_serializer.custom_options.fetch(:custom_options)
       end
 
       def test_belongs_to
@@ -159,7 +165,9 @@ module ActiveModel
 
       class NamespacedResourcesTest < ActiveSupport::TestCase
         class ResourceNamespace
-          class Post    < ::Model; end
+          class Post < ::Model
+            associations :comments, :author, :description
+          end
           class Comment < ::Model; end
           class Author  < ::Model; end
           class Description < ::Model; end
@@ -200,7 +208,9 @@ module ActiveModel
       end
 
       class NestedSerializersTest < ActiveSupport::TestCase
-        class Post    < ::Model; end
+        class Post < ::Model
+          associations :comments, :author, :description
+        end
         class Comment < ::Model; end
         class Author  < ::Model; end
         class Description < ::Model; end
@@ -240,7 +250,10 @@ module ActiveModel
 
         # rubocop:disable Metrics/AbcSize
         def test_conditional_associations
-          model = ::Model.new(true: true, false: false)
+          model = Class.new(::Model) do
+            attributes :true, :false
+            associations :association
+          end.new(true: true, false: false)
 
           scenarios = [
             { options: { if:     :true  }, included: true  },

test/serializers/attribute_test.rb

@@ -81,7 +81,7 @@ module ActiveModel
         assert_equal('custom', hash[:blog][:id])
       end
 
-      class PostWithVirtualAttribute < ::Model; end
+      class PostWithVirtualAttribute < ::Model; attributes :first_name, :last_name end
       class PostWithVirtualAttributeSerializer < ActiveModel::Serializer
         attribute :name do
           "#{object.first_name} #{object.last_name}"
@@ -98,7 +98,9 @@ module ActiveModel
 
       # rubocop:disable Metrics/AbcSize
       def test_conditional_associations
-        model = ::Model.new(true: true, false: false)
+        model = Class.new(::Model) do
+          attributes :true, :false, :attribute
+        end.new(true: true, false: false)
 
         scenarios = [
           { options: { if:     :true  }, included: true  },

test/serializers/options_test.rb

@@ -3,18 +3,29 @@ require 'test_helper'
 module ActiveModel
   class Serializer
     class OptionsTest < ActiveSupport::TestCase
-      def setup
-        @profile = Profile.new(name: 'Name 1', description: 'Description 1')
+      class ModelWithOptions < ActiveModelSerializers::Model
+        attributes :name, :description
+      end
+      class ModelWithOptionsSerializer < ActiveModel::Serializer
+        attributes :name, :description
+
+        def arguments_passed_in?
+          instance_options[:my_options] == :accessible
+        end
+      end
+
+      setup do
+        @model_with_options = ModelWithOptions.new(name: 'Name 1', description: 'Description 1')
       end
 
       def test_options_are_accessible
-        @profile_serializer = ProfileSerializer.new(@profile, my_options: :accessible)
-        assert @profile_serializer.arguments_passed_in?
+        model_with_options_serializer = ModelWithOptionsSerializer.new(@model_with_options, my_options: :accessible)
+        assert model_with_options_serializer.arguments_passed_in?
       end
 
       def test_no_option_is_passed_in
-        @profile_serializer = ProfileSerializer.new(@profile)
-        refute @profile_serializer.arguments_passed_in?
+        model_with_options_serializer = ModelWithOptionsSerializer.new(@model_with_options)
+        refute model_with_options_serializer.arguments_passed_in?
       end
     end
   end

test/serializers/serializer_for_with_namespace_test.rb

@@ -3,9 +3,12 @@ require 'test_helper'
 module ActiveModel
   class Serializer
     class SerializerForWithNamespaceTest < ActiveSupport::TestCase
-      class Book < ::Model; end
-      class Page < ::Model; end
-      class Publisher < ::Model; end
+      class Book < ::Model
+        attributes :title, :author_name
+        associations :publisher, :pages
+      end
+      class Page < ::Model; attributes :number, :text end
+      class Publisher < ::Model; attributes :name end
 
       module Api
         module V3
@@ -18,8 +21,6 @@ module ActiveModel
 
           class PageSerializer < ActiveModel::Serializer
             attributes :number, :text
-
-            belongs_to :book
           end
 
           class PublisherSerializer < ActiveModel::Serializer