looks like Drones link to composer is broken again - not related to this PR though

[Composer\Downloader\TransportException]
--
55 | Could not authenticate against github.com

@PhilETaylor Would it make sense to add some test cases for e.g. Cyrillic or Greece names, e.g. Изображений and Εικόνες?

And regarding numbers I am missing some with a number as first character. Your examples with numbers all start with /.

			array(false, $xml, '.images'),
			array(false, $xml, './images'),
			array(false, $xml, '.\images'),
			array(false, $xml, '../images'),
			array(false, $xml, '.../images'),
			array(true, $xml, 'c:\images'),
			array(false, $xml, '\\images'), // Means \images
			array(true, $xml, 'ftp://images'),
			array(true, $xml, 'http://images'),
			array(false, $xml, '/media'),
			array(false, $xml, '/administrator'),
			array(false, $xml, '/4711images'),
			array(false, $xml, '4711images'),
			array(false, $xml, '1'),
			array(false, $xml, '_'),
			array(false, $xml, '*'),
			array(false, $xml, '%'),
			array(false, $xml, '://foo'),
			array(false, $xml, '/4711i/images'),
			array(false, $xml, '../4711i/images'),
			array(false, $xml, 'Εικόνες'),
			array(false, $xml, 'Изображений'),

PHPUnit 4.8.36 by Sebastian Bergmann and contributors.
Warning:	The Xdebug extension is not loaded
		No code coverage will be generated.

......................

Time: 67 ms, Memory: 8.00MB

OK (22 tests, 22 assertions)

@PhilETaylor On Linux test are passing:

richard@vmkubu02:~/lamp/public_html/joomla-cms$ ./libraries/vendor/phpunit/phpunit/phpunit tests/unit/suites/libraries/cms/form/rule/FilePathRuleTest.php
PHPUnit 4.8.36 by Sebastian Bergmann and contributors.
Warning:        The Xdebug extension is not loaded
                No code coverage will be generated.

.......................

Time: 59 ms, Memory: 8.00MB

OK (23 tests, 23 assertions)

User deprecation notices (138)

JError::setErrorHandling() is deprecated: 138x
    69x in FilePathRuleTest::setUp
    69x in FilePathRuleTest::tearDown

richard@vmkubu02:~/lamp/public_html/joomla-cms$

Windows I haven't tested (yet).

Windows I haven't tested (yet).

Well I dont have windows anywhere here but isn't this why we have Drone and AppVeyor?

https://ci.appveyor.com/project/release-joomla/joomla-cms/builds/38276109/job/lpq1nwygs34vr7qk?fullLog=true

Thats windows, and the tests are passing there.

https://ci.appveyor.com/project/release-joomla/joomla-cms/builds/38276109/job/lpq1nwygs34vr7qk?fullLog=true

Thats windows, and the tests are passing there.

@PhilETaylor You are right, thanks for pointing me to it. I think I need sleep soon ;-)

I have tested this item ✅ successfully on b470537

Unit tests pass on Linux (drone) and Windows (appveyor).

I've successfully checked the complete loge files in drone and appveyor to verify that the new tests have been run.

I am meging this on review. The PR #32718 need some ajustments so that the test covers the b/c break as Phil pointed out, I will make a comment on the other PR how to test.