PhpSpreadsheet/tests/data/Calculation/TextData/UPPER.php

<?php

return [
    [
        'ABCDEFGHI',
        'AbCdEfGhI',
    ],
    [
        'MARK BAKER',
        'mark baker',
    ],
    [
        'TRUE',
        true,
    ],
    [
        'FALSE',
        false,
    ],
];