2 files changed, 31 insertions, 5 deletions
diff --git a/activemodel/test/cases/attribute_assignment_test.rb b/activemodel/test/cases/attribute_assignment_test.rb
index 3336691841..287bea719c 100644
--- a/activemodel/test/cases/attribute_assignment_test.rb
+++ b/activemodel/test/cases/attribute_assignment_test.rb
@@ -1,4 +1,5 @@
 require "cases/helper"
+require "active_support/core_ext/hash/indifferent_access"
 require "active_support/hash_with_indifferent_access"
 
 class AttributeAssignmentTest < ActiveModel::TestCase
@@ -23,13 +24,32 @@ class AttributeAssignmentTest < ActiveModel::TestCase
   class ErrorFromAttributeWriter < StandardError
   end
 
-  class ProtectedParams < ActiveSupport::HashWithIndifferentAccess
+  class ProtectedParams
+    attr_accessor :permitted
+    alias :permitted? :permitted
+
+    delegate :keys, :key?, :has_key?, :empty?, to: :@parameters
+
+    def initialize(attributes)
+      @parameters = attributes.with_indifferent_access
+      @permitted = false
+    end
+
     def permit!
       @permitted = true
+      self
+    end
+
+    def [](key)
+      @parameters[key]
+    end
+
+    def to_h
+      @parameters
     end
 
-    def permitted?
-      @permitted ||= false
+    def stringify_keys
+      dup
     end
 
     def dup
diff --git a/activemodel/test/cases/forbidden_attributes_protection_test.rb b/activemodel/test/cases/forbidden_attributes_protection_test.rb
index 3cb204a2c5..d8d757f52a 100644
--- a/activemodel/test/cases/forbidden_attributes_protection_test.rb
+++ b/activemodel/test/cases/forbidden_attributes_protection_test.rb
@@ -2,12 +2,14 @@ require 'cases/helper'
 require 'active_support/core_ext/hash/indifferent_access'
 require 'models/account'
 
-class ProtectedParams < ActiveSupport::HashWithIndifferentAccess
+class ProtectedParams
   attr_accessor :permitted
   alias :permitted? :permitted
 
+  delegate :keys, :key?, :has_key?, :empty?, to: :@parameters
+
   def initialize(attributes)
-    super(attributes)
+    @parameters = attributes
     @permitted = false
   end
 
@@ -15,6 +17,10 @@ class ProtectedParams < ActiveSupport::HashWithIndifferentAccess
     @permitted = true
     self
   end
+
+  def to_h
+    @parameters
+  end
 end
 
 class ActiveModelMassUpdateProtectionTest < ActiveSupport::TestCase