Love the Memcached extension, looking to do a 'lower'-level integration (which always makes me laugh in a scripting language), which requires some testing. Unfortunately, this does not seem possible with the current 2.2.0 release.
Declaration of Mock_Memcached_0376aa4c::get() should be compatible with Memcached::get($key, $cache_cb = NULL, &$cas_token = NULL, &$udf_flags = NULL)
Also see: sebastianbergmann/phpunit-mock-objects#192
Currently seen in PHP 5.5+ (tested 5.5.22 / 5.6.7), with phpunit 3.7, 4.4, 4.5