Failed asserting that an array has the key 'addplugintest'.

/home/ubuntu/code/cache/tests/config_writer_test.php:181
/home/ubuntu/code/lib/phpunit/classes/advanced_testcase.php:80

This happens with PHP5.5 and opcode caching enabled. Seems muc config file isn't read from disk, after "addplugintest" store has been added...