Add a simple XmlResponseHandlerTest

tests/Whoops/Handler/XmlResponseHandlerTest.php

@@ -0,0 +1,35 @@
+<?php
+/**
+ * Whoops - php errors for cool kids
+ */
+
+namespace Whoops\Handler;
+use Whoops\TestCase;
+use Whoops\Handler\XmlResponseHandler;
+use RuntimeException;
+
+class XmlResponseHandlerTest extends TestCase
+{
+    public function testValidXml()
+    {
+        $handler = new XmlResponseHandler;
+
+        $run = $this->getRunInstance();
+        $run->pushHandler($handler);
+        $run->register();
+
+        ob_start();
+        $run->handleException(new RuntimeException);
+        $xml = ob_get_clean();
+
+        $this->assertTrue($this->isValidXml($xml));
+    }
+
+    private function isValidXml($data)
+    {
+        $prev = libxml_use_internal_errors(true);
+        $xml = simplexml_load_string($data);
+        libxml_use_internal_errors($prev);
+        return $xml !== false;
+    }
+}