diff --git a/tool/sync_test_lib.rb b/tool/sync_test_lib.rb
new file mode 100755
index 00000000000000..d950b4994defea
--- /dev/null
+++ b/tool/sync_test_lib.rb
@@ -0,0 +1,51 @@
+#!/usr/bin/env ruby
+
+require "fileutils"
+
+test_lib_files = %w[core_assertions.rb find_executable.rb envutil.rb]
+
+repos = %w[
+  bigdecimal cgi cmath date delegate did_you_mean digest drb erb etc
+  fileutils find forwardable io-console io-nonblock io-wait ipaddr
+  irb logger net-http net-protocol open-uri open3 openssl optparse
+  ostruct pathname pstore psych racc resolv stringio strscan tempfile
+  time timeout tmpdir uri weakref win32ole yaml zlib
+]
+
+branch_name = "update-test-lib-#{Time.now.strftime("%Y%m%d")}"
+title = "Update test libraries from ruby/ruby #{Time.now.strftime("%Y-%m-%d")}"
+commit = `git rev-parse HEAD`.chomp
+message = "Update test libraries from https://github.com/ruby/ruby/commit/#{commit}"
+
+repos.each do |repo|
+  puts "#{repo}: start"
+
+  Dir.chdir("../#{repo}") do
+    if `git branch --list #{branch_name}`.empty?
+      system "git switch master"
+      system "git switch -c #{branch_name}"
+    else
+      puts "#{repo}: "
+      next
+    end
+
+    test_lib_files.each do |file|
+      FileUtils.cp("../ruby/tool/lib/#{file}", "test/lib/#{file}")
+      system "git add test/lib/#{file}"
+    end
+
+    if `git commit -m '#{message}'`.chomp =~ /nothing to commit/
+      puts "#{repo}: nothing to update"
+    else
+      system "git push"
+      system "gh repo set-default ruby/#{repo}"
+      system "gh pr create --base master --head ruby:#{branch_name} --title \"#{title}\" --body \"#{message}\""
+      puts "#{repo}: updated"
+    end
+
+    system "git switch master"
+    system "git branch -D #{branch_name}"
+  end
+rescue StandardError => e
+  ptus e
+end