1 files changed, 14 insertions, 2 deletions
diff --git a/test/fiber/scheduler.rb b/test/fiber/scheduler.rb
index af64e4ebb6..2785561000 100644
--- a/test/fiber/scheduler.rb
+++ b/test/fiber/scheduler.rb
@@ -112,8 +112,10 @@ class Scheduler
 
     self.run
   ensure
-    @urgent.each(&:close)
-    @urgent = nil
+    if @urgent
+      @urgent.each(&:close)
+      @urgent = nil
+    end
 
     @closed = true
 
@@ -240,3 +242,13 @@ class BrokenUnblockScheduler < Scheduler
     raise "Broken unblock!"
   end
 end
+
+class SleepingUnblockScheduler < Scheduler
+  # This method is invoked when the thread is exiting.
+  def unblock(blocker, fiber)
+    super
+
+    # This changes the current thread state to `THREAD_RUNNING` which causes `thread_join_sleep` to hang.
+    sleep(0.1)
+  end
+end