Mr. Serge, to test WordPress 2.8 simply change $wp_version inside /wp-includes/version.php from 2.7.1 to 2.8-bleeding-edge and do an automatic upgrade as you normally would when a new version is released.
Mr. Serge, to test WordPress 2.8 simply change $wp_version inside /wp-includes/version.php from 2.7.1 to 2.8-bleeding-edge and do an automatic upgrade as you normally would when a new version is released.