Nested foreach over ObjectStorage

output.txt

array (size=4)
  0 => string 'outer' (length=5)
  1 => string 'inner' (length=5)
  2 => string 'inner' (length=5)
  3 => string 'inner' (length=5)

test.php

<?php

use TYPO3\CMS\Extbase\Domain\Model\FrontendUser;
use TYPO3\CMS\Extbase\Persistence\ObjectStorage;

$testObjectStorage = new ObjectStorage();
$testObjectStorage->attach(new FrontendUser());
$testObjectStorage->attach(new FrontendUser());
$testObjectStorage->attach(new FrontendUser());
$executions = [];
foreach ($testObjectStorage as $feUser) {
    $executions[] = 'outer';
    foreach ($testObjectStorage as $feUser) {
        $executions[] = 'inner';
    }
}
var_dump($executions);