当所有测试运行正常时，为什么PHPUnit返回-1。
phpunit application/models2/Sima/UserTest.php
PHPUnit 3.7.29 by Sebastian Bergmann.
Configuration read from /home/bamboo/bamboo-home/xml-data/build-dir/SIMA-MAIN-JOB1/tests/phpunit.xml
.
Time: 866 ms, Memory: 19.25Mb
OK (1 test, 2 assertions)