No need to handle if FrozenError is available

Rails 6 requires Ruby 2.5, which introduces `FrozenError`
https://docs.ruby-lang.org/en/2.5.0/NEWS.html

Related to #31520

2 files changed, 1 insertions, 5 deletions

diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index a6396d3509..4242daf39a 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -255,7 +255,7 @@ module ApplicationTests
 
     test "can't change middleware after it's built" do
       boot!
-      assert_raise frozen_error_class do
+      assert_raise FrozenError do
         app.config.middleware.use Rack::Config
       end
     end
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index 39c936428f..4523b66dda 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -462,10 +462,6 @@ class ActiveSupport::TestCase
   include TestHelpers::Generation
   include ActiveSupport::Testing::Stream
   include ActiveSupport::Testing::MethodCallAssertions
-
-  def frozen_error_class
-    Object.const_defined?(:FrozenError) ? FrozenError : RuntimeError
-  end
 end
 
 # Create a scope and build a fixture rails app