Run tests with Rails default configuration to enable Zeitwerk

spec/test_app/config/application.rb

@@ -9,7 +9,7 @@
 module TestApp
   class Application < Rails::Application
     # Initialize configuration defaults for originally generated Rails version.
-    # config.load_defaults 6.0
+    config.load_defaults Gem::Version.new(Rails.version).segments.slice(0..1).join('.').to_f
 
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration can go into files in config/initializers

spec/test_app/config/initializers/good_job.rb

@@ -1,12 +1,3 @@
-if ENV['RBTRACE']
-  require 'sigdump/setup'
-  require 'rbtrace'
-  sleep 1
-  $stdout.puts "Run $ bundle exec rbtrace --pid #{Process.pid} --firehose"
-  $stdout.puts 'Press Enter to continue'
-  $stdin.gets
-end
-
 if ENV['GOOD_JOB_EXECUTION_MODE'].present?
   ActiveJob::Base.queue_adapter = :good_job
 end

spec/test_app/config/initializers/rbtrace.rb

@@ -0,0 +1,10 @@
+if ENV['RBTRACE']
+  require 'sigdump/setup'
+  require 'rbtrace'
+  sleep 1
+  $stdout.puts "Enabled rbtrace. Example commands:"
+  $stdout.puts "  Show all method calls: $ bundle exec rbtrace --pid #{Process.pid} --firehose"
+  $stdout.puts "  Debug Rails deadlock: $ bundle exec rbtrace --pid #{Process.pid} --eval \"puts output = ActionDispatch::DebugLocks.new(nil).send(:render_details, nil); output\""
+  $stdout.puts 'Press Enter to continue...'
+  $stdin.gets
+end