Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

crates/nu-command/tests/commands/random/uuid.rs

@@ -0,0 +1,16 @@
+use nu_test_support::{nu, pipeline};
+use uuid_crate::Uuid;
+
+#[test]
+fn generates_valid_uuid4() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        random uuid
+        "#
+    ));
+
+    let result = Uuid::parse_str(actual.out.as_str());
+
+    assert!(result.is_ok());
+}