unify tests for all compression extensions

src/globals/ext-tests/xz.php

@@ -2,7 +2,14 @@
 
 declare(strict_types=1);
 
-$str = 'Data you would like compressed.';
 assert(function_exists('xzencode'));
 assert(function_exists('xzdecode'));
-assert(xzdecode(xzencode($str)) === $str);
+
+$input = str_repeat('The quick brown fox jumps over the lazy dog. ', 10);
+$compressed = xzencode($input);
+assert(is_string($compressed));
+assert(strlen($compressed) < strlen($input));
+
+$uncompressed = xzdecode($compressed);
+assert(is_string($uncompressed));
+assert($uncompressed === $input);