How to access get method in a Test Class Symfony2

I have to write a test class to test my service methods. In my controllers I could access the service by doing $service = $this->get('myService'); and I could access my methods by doing $service->someMethod();.

Now I want to write a test class to test some of the service methods, I tried doing like the doc :

class ServiceTest extends \PHPUnit_Framework_TestCase {
    public function testSomeMethod() {
        $service = $this->get('myService');
        ....
    }
}

When I launch the test I get something like :

Fatal error : Call to undefined method XXX\XXXBundle\Tests\Services\ServicesTest::get() in ...

So my question is how can I use get method to be able to call my service methods