ZVAL_STRINGL please work

tests/HashTest.php

@@ -0,0 +1,20 @@
+<?php
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+use AWS\CRT\CRT;
+use AWS\CRT\Cal\Hash;
+
+require_once('common.inc');
+
+final class HashTest extends CrtTestCase {
+
+    public function testSha256Empty() {
+        $h = Hash::sha256_new();
+        $digest = $h->digest(0);
+        $expected = '\xe3\xb0\xc4\x42\x98\xfc\x1c\x14\x9a\xfb\xf4\xc8\x99\x6f\xb9\x24\x27\xae\x41\xe4\x64\x9b\x93\x4c\xa4\x95\x99\x1b\x78\x52\xb8\x55';
+        // $expected = 'test2';
+        $this->assertEquals($expected, $digest);
+    }
+}