PHPUnit_Framework_Assert::callback PHP Method

    public static function callback($callback)
    {
        return new PHPUnit_Framework_Constraint_Callback($callback);
    }

 /**
  * @covers PHPUnit_Framework_Constraint_Callback
  * @expectedException InvalidArgumentException
  * @expectedExceptionMessage Specified callback <Framework_ConstraintTest::invalid callback> is not callable.
  */
 public function testConstraintCallbackInvalidArrayArgumentWithClassname()
 {
     PHPUnit_Framework_Assert::callback(array('Framework_ConstraintTest', 'invalid callback'));
 }