Update tests

tests/open_xml.txt

@@ -1,3 +1,3 @@
 cd tests
-open tests\test.xml | get rss.channel.item.link | echo $it
+open test.xml | get rss.channel.item.link | echo $it
 exit

tests/tests.rs

@@ -64,6 +64,11 @@ mod tests {
         test_helper("open_json");
     }
 
+    #[test]
+    fn open_xml() {
+        test_helper("open_xml");
+    }
+
     #[test]
     fn json_roundtrip() {
         test_helper("json_roundtrip");