test/ruby/test_process.rb: get rid of timing issue

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61476 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_process.rb

@@ -676,14 +676,17 @@ class TestProcess < Test::Unit::TestCase
         return
       end
       IO.popen([RUBY, '-e', <<-'EOS']) {|io|
+        STDOUT.sync = true
         trap(:USR1) { print "trap\n" }
+        puts "start"
         system("cat", :in => "fifo")
       EOS
-        sleep 1
+        assert_equal("start\n", io.gets)
+        sleep 0.2 # wait for the child to stop at opening "fifo"
         Process.kill(:USR1, io.pid)
-        sleep 1
+        assert_equal("trap\n", io.readpartial(8))
         File.write("fifo", "ok\n")
-        assert_equal("trap\nok\n", io.read)
+        assert_equal("ok\n", io.read)
       }
     }
   end unless windows? # does not support fifo