Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

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

@@ -0,0 +1,16 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn table_to_toml_text_and_from_toml_text_back_into_table() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            open cargo_sample.toml
+            | to toml
+            | from toml
+            | get package.name
+        "#
+    ));
+
+    assert_eq!(actual.out, "nu");
+}