Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

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

@@ -0,0 +1,28 @@
+use nu_test_support::fs::Stub::FileWithContentToBeTrimmed;
+use nu_test_support::playground::Playground;
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn to_row() {
+    Playground::setup("split_row_test_1", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "sample.txt",
+            r#"
+                importer,shipper,tariff_item,name,origin
+            "#,
+        )]);
+
+        let actual = nu!(
+            cwd: dirs.test(), pipeline(
+            r#"
+                open sample.txt
+                | lines
+                | str trim
+                | split row ","
+                | length
+            "#
+        ));
+
+        assert!(actual.out.contains('5'));
+    })
+}