Update docs/languages/en/user-guide/unit-testing.rst

assertModule to assertModuleName. Was changed in commit fa71329a155ec3ae5bdc045ac74d26c98365432b (https://github.com/zendframework/zf2/commit/fa71329a155ec3ae5bdc045ac74d26c98365432b#library/Zend/Test/PHPUnit)/Controller/AbstractControllerTestCase.php