From 3127e99d6e0d89149dca5c4815474b69012a86b7 Mon Sep 17 00:00:00 2001
From: Matthew Draper <matthew@trebex.net>
Date: Fri, 7 Oct 2016 09:28:36 +1030
Subject: Simplify serializable test to avoid mystery deadlock

---
 .../cases/adapters/postgresql/transaction_test.rb  | 44 +++++++++++-----------
 1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/activerecord/test/cases/adapters/postgresql/transaction_test.rb b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
index 00119f13bb..c450524de8 100644
--- a/activerecord/test/cases/adapters/postgresql/transaction_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
@@ -28,32 +28,29 @@ module ActiveRecord
     end
 
     test "raises SerializationFailure when a serialization failure occurs" do
-      with_warning_suppression do
-        assert_raises(ActiveRecord::SerializationFailure) do
-          thread = Thread.new do
-            Sample.transaction isolation: :serializable do
-              Sample.delete_all
+      assert_raises(ActiveRecord::SerializationFailure) do
+        before = Concurrent::CyclicBarrier.new(2)
+        after = Concurrent::CyclicBarrier.new(2)
 
-              10.times do |i|
-                sleep 0.1
-
-                Sample.create value: i
-              end
+        thread = Thread.new do
+          with_warning_suppression do
+            Sample.transaction isolation: :serializable do
+              before.wait
+              Sample.create value: Sample.sum(:value)
+              after.wait
             end
           end
+        end
 
-          sleep 0.1
-
-          Sample.transaction isolation: :serializable do
-            Sample.delete_all
-
-            10.times do |i|
-              sleep 0.1
-
-              Sample.create value: i
+        begin
+          with_warning_suppression do
+            Sample.transaction isolation: :serializable do
+              before.wait
+              Sample.create value: Sample.sum(:value)
+              after.wait
             end
           end
-
+        ensure
           thread.join
         end
       end
@@ -91,10 +88,11 @@ module ActiveRecord
     protected
 
       def with_warning_suppression
-        log_level = @connection.client_min_messages
-        @connection.client_min_messages = "error"
+        log_level = ActiveRecord::Base.connection.client_min_messages
+        ActiveRecord::Base.connection.client_min_messages = "error"
         yield
-        @connection.client_min_messages = log_level
+      ensure
+        ActiveRecord::Base.connection.client_min_messages = log_level
       end
   end
 end
-- 
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