ClassToTestA.php

<?php

class ClassToTestA
{
    public function __construct(private ClockInterface $clock) {}
    
    public function do(): void
    {
        $a = $this->clock->now();
        sleep(6);
        $b = $this->clock->now();
        
        if ($b->getTimestamp() - $a->getTimestamp() != 6) {
            throw new Exception('broken');
        }
    }
}

ClassToTestB.php

<?php

class ClassToTestB
{
  public function __construct(
    private ClockInterface $clock,
    private SleepInterface $sleep,
  ) {}
  
  public function do(): void
  {
    $a = $this->clock->now();
    $this->sleeper->sleep(6)
    $b = $this->clock->now();
    
    if ($b->getTimestamp() - $a->getTimestamp() != $this->sleeper->getSleep()) {
      throw new Exception('broken');
    }
  }
}

MockSleeper.php

<?php

class MockSleeper implements SleepInterface
{
  public function __construct(private int $sleep) {}
  
  public function sleep(int $sleep): void
  {
    // do nothing
  }
  
  public function getSleep(): int
  {
    return $this->sleep;
  }
}

test.php

<?php

$mock = new MockClock([
  new DateTimeImmutable('2022-06-21T12:23:34.000000Z'),
  new DateTimeImmutable('2022-06-21T12:23:40.000000Z'),
]);

$foo = new ClassToTestA($mock);

$foo->do();

$bar = new ClassToTestB($mock, new MockSleeper(6));