add test for default constructor

Author: dbu

tests/DefaultHttpAdapterTest.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Http\Adapter\Guzzle6\Tests;
+
+use Http\Adapter\Guzzle6\Client;
+use Http\Client\Tests\HttpClientTest;
+
+/**
+ * @author David Buchmann <[email protected]>
+ */
+class DefaultHttpAdapterTest extends HttpClientTest
+{
+    /**
+     * {@inheritdoc}
+     */
+    protected function createHttpAdapter()
+    {
+        return new Client();
+    }
+}