Handle `Timeout::Error` reported from workers

tool/lib/test/unit.rb

@@ -1065,7 +1065,7 @@ module Test
             runner.add_status(" = #$1")
           when /\A\.+\z/
             runner.succeed
-          when /\A\.*[EFS][EFS.]*\z/
+          when /\A\.*[EFST][EFST.]*\z/
             runner.failed(s)
           else
             $stdout.print(s)

tool/test/testunit/test4test_timeout.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+$LOAD_PATH.unshift "#{File.dirname(__FILE__)}/../../lib"
+
+require 'test/unit'
+require 'timeout'
+
+class TestForTestTimeout < Test::Unit::TestCase
+  10.times do |i|
+    define_method("test_timeout_#{i}") do
+      Timeout.timeout(0.001) do
+        sleep
+      end
+    end
+  end
+end

tool/test/testunit/test_timeout.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: false
+require 'test/unit'
+
+class TestTiemout < Test::Unit::TestCase
+  def test_timeout
+    cmd = [*@options[:ruby], "#{File.dirname(__FILE__)}/test4test_timeout.rb"]
+    result = IO.popen(cmd, err: [:child, :out], &:read)
+    assert_not_match(/^T{10}$/, result)
+  end
+end