Cache Status info don't appear on HTML footer

I was supposed to get something like this in footer:

<!– Dynamic page generated in 0.450 seconds. –>
<!– Cached page generated by WP-Super-Cache on 2013-02-14 16:37:28 –>
<!– super cache –>

This option is enabled in Debug, however, I didn’t get this. Is there any other way to test if the cache is working?

http://wordpress.org/extend/plugins/wp-super-cache/