split dummy classes in tests into their own file

tests/PartialWrapper.php

@@ -0,0 +1,38 @@
+<?php
+/**
+ * @copyright Copyright (c) 2020 Robin Appelman <robin@icewind.nl>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace Icewind\Streams\Tests;
+
+class PartialWrapper extends \Icewind\Streams\NullWrapper {
+    public static function wrap($source) {
+        return self::wrapSource($source);
+    }
+
+    public function stream_read($count) {
+        $count = min($count, 2); // return as most 2 bytes
+        return parent::stream_read($count);
+    }
+
+    public function stream_write($data) {
+        $data = substr($data, 0, 2); //write as most 2 bytes
+        return parent::stream_write($data);
+    }
+}