3 files changed, 100 insertions, 11 deletions
diff --git a/railties/test/application/zeitwerk_integration_test.rb b/railties/test/application/zeitwerk_integration_test.rb
index dc6db429a9..40d06ee999 100644
--- a/railties/test/application/zeitwerk_integration_test.rb
+++ b/railties/test/application/zeitwerk_integration_test.rb
@@ -98,24 +98,35 @@ class ZeitwerkIntegrationTest < ActiveSupport::TestCase
     assert_nil deps.safe_constantize("Admin")
   end
 
-  test "autoloaded_constants returns autoloaded constant paths" do
-    app_file "app/models/admin/user.rb", "class Admin::User; end"
+  test "to_unload? says if a constant would be unloaded (main)" do
+    app_file "app/models/user.rb", "class User; end"
     app_file "app/models/post.rb", "class Post; end"
     boot
 
-    assert Admin::User
-    assert_equal ["Admin", "Admin::User"], deps.autoloaded_constants
+    assert Post
+    assert deps.to_unload?("Post")
+    assert_not deps.to_unload?("User")
   end
 
-  test "autoloaded? says if a constant has been autoloaded" do
+  test "to_unload? says if a constant would be unloaded (once)" do
+    add_to_config 'config.autoload_once_paths << "#{Rails.root}/extras"'
+    app_file "extras/foo.rb", "class Foo; end"
+    app_file "extras/bar.rb", "class Bar; end"
+    boot
+
+    assert Foo
+    assert_not deps.to_unload?("Foo")
+    assert_not deps.to_unload?("Bar")
+  end
+
+  test "to_unload? says if a constant would be unloaded (reloading disabled)" do
     app_file "app/models/user.rb", "class User; end"
     app_file "app/models/post.rb", "class Post; end"
-    boot
+    boot("production")
 
     assert Post
-    assert deps.autoloaded?("Post")
-    assert deps.autoloaded?(Post)
-    assert_not deps.autoloaded?("User")
+    assert_not deps.to_unload?("Post")
+    assert_not deps.to_unload?("User")
   end
 
   test "eager loading loads the application code" do
@@ -131,6 +142,29 @@ class ZeitwerkIntegrationTest < ActiveSupport::TestCase
     assert $zeitwerk_integration_test_post
   end
 
+  test "reloading is enabled if config.cache_classes is false" do
+    boot
+
+    assert     Rails.autoloaders.main.reloading_enabled?
+    assert_not Rails.autoloaders.once.reloading_enabled?
+  end
+
+  test "reloading is disabled if config.cache_classes is true" do
+    boot("production")
+
+    assert_not Rails.autoloaders.main.reloading_enabled?
+    assert_not Rails.autoloaders.once.reloading_enabled?
+  end
+
+  test "reloading raises if config.cache_classes is true" do
+    boot("production")
+
+    e = assert_raises(StandardError) do
+      deps.clear
+    end
+    assert_equal "reloading is disabled because config.cache_classes is true", e.message
+  end
+
   test "eager loading loads code in engines" do
     $test_blog_engine_eager_loaded = false
 
@@ -301,4 +335,46 @@ class ZeitwerkIntegrationTest < ActiveSupport::TestCase
       assert_nil autoloader.logger
     end
   end
+
+  # This is here because to guarantee classic mode works as always, Zeitwerk
+  # integration does not touch anything in classic. The descendants tracker is a
+  # very small one-liner exception. We leave its main test suite untouched, and
+  # add some minimal safety net here.
+  #
+  # When time passes, things are going to be reorganized (famous last words).
+  test "descendants tracker" do
+    class ::ZeitwerkDTIntegrationTestRoot
+      extend ActiveSupport::DescendantsTracker
+    end
+    class ::ZeitwerkDTIntegrationTestChild < ::ZeitwerkDTIntegrationTestRoot; end
+    class ::ZeitwerkDTIntegrationTestGrandchild < ::ZeitwerkDTIntegrationTestChild; end
+
+    begin
+      app_file "app/models/user.rb", "class User < ZeitwerkDTIntegrationTestRoot; end"
+      app_file "app/models/post.rb", "class Post < ZeitwerkDTIntegrationTestRoot; end"
+      app_file "app/models/tutorial.rb", "class Tutorial < Post; end"
+      boot
+
+      assert User
+      assert Tutorial
+
+      direct_descendants = [ZeitwerkDTIntegrationTestChild, User, Post].to_set
+      assert_equal direct_descendants, ZeitwerkDTIntegrationTestRoot.direct_descendants.to_set
+
+      descendants = direct_descendants.merge([ZeitwerkDTIntegrationTestGrandchild, Tutorial])
+      assert_equal descendants, ZeitwerkDTIntegrationTestRoot.descendants.to_set
+
+      ActiveSupport::DescendantsTracker.clear
+
+      direct_descendants = [ZeitwerkDTIntegrationTestChild].to_set
+      assert_equal direct_descendants, ZeitwerkDTIntegrationTestRoot.direct_descendants.to_set
+
+      descendants = direct_descendants.merge([ZeitwerkDTIntegrationTestGrandchild])
+      assert_equal descendants, ZeitwerkDTIntegrationTestRoot.descendants.to_set
+    ensure
+      Object.send(:remove_const, :ZeitwerkDTIntegrationTestRoot)
+      Object.send(:remove_const, :ZeitwerkDTIntegrationTestChild)
+      Object.send(:remove_const, :ZeitwerkDTIntegrationTestGrandchild)
+    end
+  end
 end
diff --git a/railties/test/generators/actions_test.rb b/railties/test/generators/actions_test.rb
index 44d4e92256..d913bb5438 100644
--- a/railties/test/generators/actions_test.rb
+++ b/railties/test/generators/actions_test.rb
@@ -200,7 +200,7 @@ class ActionsTest < Rails::Generators::TestCase
     run_generator
 
     action :environment do
-      _ = "# This wont be added"# assignment to silence parse-time warning "unused literal ignored"
+      _ = "# This wont be added" # assignment to silence parse-time warning "unused literal ignored"
       "# This will be added"
     end
 
diff --git a/railties/test/railties/engine_test.rb b/railties/test/railties/engine_test.rb
index 69f6e34d58..fe5c62c07d 100644
--- a/railties/test/railties/engine_test.rb
+++ b/railties/test/railties/engine_test.rb
@@ -879,7 +879,7 @@ YAML
       assert Bukkits::Engine.config.bukkits_seeds_loaded
     end
 
-    test "jobs are ran inline while loading seeds" do
+    test "jobs are ran inline while loading seeds with async adapter configured" do
       app_file "db/seeds.rb", <<-RUBY
         Rails.application.config.seed_queue_adapter = ActiveJob::Base.queue_adapter
       RUBY
@@ -891,6 +891,19 @@ YAML
       assert_instance_of ActiveJob::QueueAdapters::AsyncAdapter, ActiveJob::Base.queue_adapter
     end
 
+    test "jobs are ran with original adapter while loading seeds with custom adapter configured" do
+      app_file "db/seeds.rb", <<-RUBY
+        Rails.application.config.seed_queue_adapter = ActiveJob::Base.queue_adapter
+      RUBY
+
+      boot_rails
+      Rails.application.config.active_job.queue_adapter = :delayed_job
+      Rails.application.load_seed
+
+      assert_instance_of ActiveJob::QueueAdapters::DelayedJobAdapter, Rails.application.config.seed_queue_adapter
+      assert_instance_of ActiveJob::QueueAdapters::DelayedJobAdapter, ActiveJob::Base.queue_adapter
+    end
+
     test "skips nonexistent seed data" do
       FileUtils.rm "#{app_path}/db/seeds.rb"
       boot_rails