Testing duration of Unittests

Code
<?php

use PHPUnit\Framework\TestCase;

class 
TimeTest extends TestCase
{
    public function 
testInTime() : void
    
{
        
// testing duration of a script is not
        // a good test method since runtime can be
        // affected by other causes.
        
PHP_Timer::start();
        
sleep(1);
        
$time PHP_Timer::stop();
        
        
$message sprintf('execution time was %s',
            
PHP_Timer::secondsToTimeString($time));
        
        
$this->assertLessThan(0$time$message);
    }
}
Result
Time: 203 ms, Memory: 10.00 MB

There was 1 error:

1) TimeTest::testInTime
Class 'PHP_Timer' not found

PhpunitExec.php:22

ERRORS!
Tests: 1, Assertions: 0, Errors: 1.
Used Versions
PHP 7.3, Zend 3.0, Symfony 4.3, Laravel 5.8, PHPUnit 8.0, Doctrine 2.10