You must set the following environment variables to run the tests: PDO_MYSQL_TEST_DSN - DSN For example: mysql:dbname=test;host=localhost;port=3306 PDO_MYSQL_TEST_HOST - database host PDO_MYSQL_TEST_DB - database (schema) name PDO_MYSQL_TEST_SOCKET - database server socket PDO_MYSQL_TEST_ENGINE - storage engine to use PDO_MYSQL_TEST_USER - database user PDO_MYSQL_TEST_PASS - database user password PDO_MYSQL_TEST_CHARSET - database charset NOTE: if any of PDO_MYSQL_TEST_[HOST|DB|SOCKET|ENGINE|CHARSET] is part of PDO_MYSQL_TEST_DSN, the values must match. That is, for example, for PDO_MYSQL_TEST_DSN = mysql:dbname=test you MUST set PDO_MYSQL_TEST_DB=test.