Ctestcase. How Can Change Property?

There is a test.

class CMethodTest extends CTestCase{

    public $a = 1;

    public static function setUpBeforeClass(){



    public function testZ(){

        $this->a = 'z';


    public function testAb(){

        $this->a = 'b';


    public function testE(){




The test has 3 methods. Inside these methods $this->a is trying to change. As a result $this->a equal "1".

Why Can not i change $this->a?

For each test, when it starts, ‘a’ takes back the value 1.

you can call all of your methods in same test and it’ll work.