From 4e79deeccefa761934067a72aba4cde280316acf Mon Sep 17 00:00:00 2001
From: Katsuya HIDAKA <hidakatsuya@gmail.com>
Date: Sat, 23 May 2026 02:56:17 +0900
Subject: Fix flaky IssueNestedSetConcurrencyTest

---
 .../unit/issue_nested_set_concurrency_test.rb | 32 ++++++++++++-------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/test/unit/issue_nested_set_concurrency_test.rb b/test/unit/issue_nested_set_concurrency_test.rb
index 2692ce99f..54459ebf3 100644
--- a/test/unit/issue_nested_set_concurrency_test.rb
+++ b/test/unit/issue_nested_set_concurrency_test.rb
@@ -23,6 +23,7 @@ class IssueNestedSetConcurrencyTest < ActiveSupport::TestCase
   self.use_transactional_tests = false
 
   def setup
+    @connection_pool_mutex = Mutex.new
     skip if sqlite?
     if mysql?
       connection = ActiveRecord::Base.connection_db_config.configuration_hash.deep_dup
@@ -87,14 +88,14 @@ class IssueNestedSetConcurrencyTest < ActiveSupport::TestCase
       threads = []
       ids_to_remove.each_slice(10) do |ids|
         threads << Thread.new do
-          ActiveRecord::Base.connection_pool.with_connection do
-            begin
+          begin
+            with_thread_connection do
               ids.each do |id|
                 Issue.find(id).update(parent_id: nil)
               end
-            rescue => e
-              Thread.current[:exception] = e.message
             end
+          rescue => e
+            Thread.current[:exception] = e.message
           end
         end
       end
@@ -118,17 +119,15 @@ class IssueNestedSetConcurrencyTest < ActiveSupport::TestCase
 
   private
 
-  def threaded(count, &)
+  def threaded(count, &block)
     with_settings :notified_events => [] do
       threads = []
       count.times do |i|
         threads << Thread.new(i) do
-          ActiveRecord::Base.connection_pool.with_connection do
-            begin
-              yield
-            rescue => e
-              Thread.current[:exception] = e.message
-            end
+          begin
+            with_thread_connection(&block)
+          rescue => e
+            Thread.current[:exception] = e.message
           end
         end
       end
@@ -138,4 +137,15 @@ class IssueNestedSetConcurrencyTest < ActiveSupport::TestCase
       end
     end
   end
+
+  def with_thread_connection(&)
+    # Active Record updates its connection lease registry when a thread obtains a
+    # connection for the first time, which can race when test threads start
+    # together.
+    @connection_pool_mutex.synchronize do
+      # Initialize this thread's connection lease before concurrent updates.
+      ActiveRecord::Base.connection_pool.with_connection { nil }
+    end
+    ActiveRecord::Base.connection_pool.with_connection(&)
+  end
 end
-- 
2.52.0