public function test_grep_2() { // Destructive callback $arr = array('snowball', 'snowcone', 'snowangel', 'igloo', 'ice'); Enumerator::grep_($arr, "/^snow/", function ($key, &$value) { $value .= '_'; return; }); $this->assertEquals(array('snowball_', 'snowcone_', 'snowangel_'), $arr); }