Testing duration of Unittests

Code
<?php

class TimeTest extends PHPUnit_Framework_TestCase
{
    public function 
testInTime()
    {
        
// 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: 1.18 seconds, Memory: 2.00MB

There was 1 failure:

1) TimeTest::testInTime
execution time was 1 second
Failed asserting that 1.0001609325408936 is less than 0.

TimeTest.php:17

FAILURES!
Tests: 1, Assertions: 0, Failures: 1.
Used Versions
PHP 7.1, Zend 3.0, Symfony 3.2, Laravel 5.2, PHPUnit 5.6, Doctrine 2.6