Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

crates/nu-command/tests/format_conversions/xml.rs

@@ -0,0 +1,16 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn table_to_xml_text_and_from_xml_text_back_into_table() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            open jonathan.xml
+            | to xml
+            | from xml
+            | get rss.children.channel.children.0.3.item.children.guid.4.attributes.isPermaLink
+        "#
+    ));
+
+    assert_eq!(actual.out, "true");
+}