Add deprecator to the application's deprecators

test/rails_test.rb

@@ -8,4 +8,10 @@ class RailsTest < ActiveSupport::TestCase
     assert_equal :load_config_initializers, initializer.after
     assert_equal :build_middleware_stack, initializer.before
   end
+
+  if Devise::Test.rails71_and_up?
+    test 'deprecator is added to application deprecators' do
+      assert_not_nil Rails.application.deprecators[:devise]
+    end
+  end
 end