add lz4 test

src/globals/ext-tests/lz4.php

@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+assert(function_exists('lz4_compress'));
+assert(function_exists('lz4_uncompress'));
+
+$input = str_repeat('The quick brown fox jumps over the lazy dog. ', 10);
+$compressed = lz4_compress($input);
+assert(is_string($compressed));
+assert(strlen($compressed) < strlen($input));
+
+$uncompressed = lz4_uncompress($compressed);
+assert(is_string($uncompressed));
+assert($uncompressed === $input);