Add tests for special domain name

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

tests/lib/DB/ConnectionFactoryTest.php

@@ -31,9 +31,11 @@ class ConnectionFactoryTest extends TestCase {
 		return [
 			['127.0.0.1', ['host' => '127.0.0.1']],
 			['db.example.org', ['host' => 'db.example.org']],
+			['unix', ['host' => 'unix']],
 			['[::1]', ['host' => '[::1]']],
 			['127.0.0.1:3306', ['host' => '127.0.0.1', 'port' => 3306]],
 			['db.example.org:3306', ['host' => 'db.example.org', 'port' => 3306]],
+			['unix:3306', ['host' => 'unix', 'port' => 3306]],
 			['[::1]:3306', ['host' => '[::1]', 'port' => 3306]],
 			['unix:/socket', ['host' => 'unix', 'unix_socket' => '/socket']],
 		];