TYPO3 Core

A possible test for this - haven't figured out how to solve it yet:

    /**
     * @test
     */
    public function fixPermissionsUsesProperPermissionString() {
        if (TYPO3_OS == 'WIN') {
            $this->markTestSkipped('fixPermissions() tests not available on Windows');
        }

            // Create and prepare test file
        $filename = PATH_site . 'typo3temp/' . uniqid('test_');
        t3lib_div::writeFileToTypo3tempDir($filename, '42');
        chmod($filename, 0742);

            // Set target permissions and run method
        $GLOBALS['TYPO3_CONF_VARS']['BE']['fileCreateMask'] = 0660;
        $fixPermissionsResult = t3lib_div::fixPermissions($filename);

            // Get actual permissions and clean up
        clearstatcache();
        debug(decoct(fileperms($filename)));
        $resultFilePermissions = substr(decoct(fileperms($filename)), 2);
        unlink($filename);

            // Test if everything was ok
        $this->assertTrue($fixPermissionsResult);
        $this->assertEquals($resultFilePermissions, '0660');
    }

Patch set 1 for branch master of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/44430

Applied in changeset d551921bdc4c145018187e30921b015f8e8ba545.