<?php
class Errorcode
{
  const NAME_IS_NULL = 0;
}
class User
{
  public $name;
  public function __construct($name)
  {
    $this->name=$name;
  }
  public function Isempty()
  {
    try{
      if(empty($this->name))
      {
        throw new Exception('its null',Errorcode::NAME_IS_NULL);
      }
    }catch(Exception $e){
      return $e->getMessage();
    }
    return 'welcome '.$this->name;
  }
}

<?php
use PHPUnit\Framework\TestCase;
class UserTest extends TestCase
{
  protected $user;
  public function setUp()
  {
    $this->user = new User('');
  }
  public function testIsempty()
  {
    $this->user->name='mark';
    $result =$this->user->Isempty();
    $this->assertEquals('welcome mark',$result);
    $this->user->name='';
    $results =$this->user->Isempty();
    $this->assertEquals('its null',$results);
  }
}

<?php
function __autoload($class){
  include $class.'.php';
}
spl_autoload_register('__autoload');

phpunit --bootstrap src/autoload.php tests/UserTest

<phpunit bootstrap="src/autoload.php">
</phpunit>

phpunit tests/UserTest

phpunit tests