change content value

Testing with Fileutils.touch needs to call `sleep` to change the value of
mtime

Signed-off-by: Yuta Iwama <ganmacs@gmail.com>

test/plugin/in_tail/test_position_file.rb

@@ -67,15 +67,15 @@ def write_data(f, content)
       pf = Fluent::Plugin::TailInput::PositionFile.new(@file, logger: $log)
 
       mock.proxy(pf).fetch_compacted_entries do |r|
-        FileUtils.touch(@file.path) # change mtime
+        @file.write("unwatched\t#{UNWATCHED_STR}\t0000000000000000\n")
         r
       end
 
       pf.try_compact
 
       @file.seek(0)
       lines = @file.readlines
-      assert_equal 4, lines.size
+      assert_equal 5, lines.size
     end
   end