Call scheduler.block instead of scheduler.kernel_sleep for blocking Queue/SizedQueue operations

* scheduler.unblock was already already called before but with no corresponding scheduler.block
* add test that Queue#pop makes the scheduler wait until it gets an element.

1 files changed, 2 insertions, 1 deletions

diff --git a/test/fiber/scheduler.rb b/test/fiber/scheduler.rb
index 1e7f60cdf0..f7a773ade1 100644
--- a/test/fiber/scheduler.rb
+++ b/test/fiber/scheduler.rb
@@ -93,6 +93,7 @@ class Scheduler
     end
   ensure
     @urgent.each(&:close)
+    @urgent = nil
   end
 
   def current_time
@@ -139,7 +140,7 @@ class Scheduler
     end
 
     if io = @urgent&.last
-      @urgent.last.write_nonblock('.')
+      io.write_nonblock('.')
     end
   end