Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

crates/nu-command/tests/commands/def.rs

@@ -0,0 +1,22 @@
+use nu_test_support::nu;
+use nu_test_support::playground::Playground;
+use std::fs;
+
+// FIXME: jt: needs more work
+#[ignore]
+#[test]
+fn def_with_comment() {
+    Playground::setup("def_with_comment", |dirs, _| {
+        let data = r#"
+#My echo
+def e [arg] {echo $arg}
+            "#;
+        fs::write(dirs.root().join("def_test"), data).expect("Unable to write file");
+        let actual = nu!(
+            cwd: dirs.root(),
+            "source def_test; help e | to json"
+        );
+
+        assert!(actual.out.contains("My echo\\n\\n"));
+    });
+}