Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

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

@@ -0,0 +1,13 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn rolls_4_roll() {
+    let actual = nu!(
+        cwd: ".", pipeline(
+        r#"
+        random dice -d 4 -s 10 | length
+        "#
+    ));
+
+    assert_eq!(actual.out, "4");
+}