Compute entity change set in Doctrine

$unitOfWork = $this->entityManager->getUnitOfWork();
$unitOfWork->computeChangeSets();
$changeSet = $unitOfWork->getEntityChangeSet($client);

foreach ($changeSet as $fieldName => $changes) {
  $oldValue = $changes[0];
  $newValue = $changes[1];

  dump(sprintf(
    'The field "%s" changed from "%s" to "%s"',
    $fieldName,
    $oldValue,
    $newValue,
  ));
}