test: concurrency for the transaction (#336)

test/test_concurrency.rb

@@ -54,6 +54,32 @@ def test_forking_with_pipelining
     MAX_THREADS.times { |i| assert_equal(WANT, @client.call('GET', "key#{i}")) }
   end
 
+  def test_forking_with_transaction
+    skip("fork is not available on #{RUBY_ENGINE}") if %w[jruby truffleruby].include?(RUBY_ENGINE)
+
+    @client.call('SET', '{key}1', WANT)
+
+    pids = Array.new(MAX_THREADS) do
+      Process.fork do
+        @client.multi(watch: %w[{key}1]) do |tx|
+          ATTEMPTS.times do
+            MAX_THREADS.times do
+              tx.call('INCR', '{key}1')
+              tx.call('DECR', '{key}1')
+            end
+          end
+        end
+      end
+    end
+
+    pids.each do |pid|
+      _, status = Process.waitpid2(pid)
+      assert_predicate(status, :success?)
+    end
+
+    assert_equal(WANT, @client.call('GET', '{key}1'))
+  end
+
   def test_threading
     threads = Array.new(MAX_THREADS) do
       Thread.new do
@@ -84,6 +110,28 @@ def test_threading_with_pipelining
     MAX_THREADS.times { |i| assert_equal(WANT, @client.call('GET', "key#{i}")) }
   end
 
+  def test_threading_with_transaction
+    @client.call('SET', '{key}1', WANT)
+
+    threads = Array.new(MAX_THREADS) do
+      Thread.new do
+        @client.multi(watch: %w[{key}1]) do |tx|
+          ATTEMPTS.times do
+            MAX_THREADS.times do
+              tx.call('INCR', '{key}1')
+              tx.call('DECR', '{key}1')
+            end
+          end
+        end
+      rescue StandardError => e
+        e
+      end
+    end
+
+    threads.each { |t| refute_instance_of(StandardError, t.value) }
+    assert_equal(WANT, @client.call('GET', '{key}1'))
+  end
+
   private
 
   def new_test_client