Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

crates/nu-command/tests/commands/path/split.rs

@@ -0,0 +1,48 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn splits_empty_path() {
+    let actual = nu!(
+        cwd: "tests", pipeline(
+        r#"
+            echo '' | path split
+        "#
+    ));
+
+    assert_eq!(actual.out, "");
+}
+
+#[test]
+fn splits_correctly_single_path() {
+    let actual = nu!(
+        cwd: "tests", pipeline(
+        r#"
+            'home/viking/spam.txt'
+            | path split
+            | last
+        "#
+    ));
+
+    assert_eq!(actual.out, "spam.txt");
+}
+
+#[test]
+fn splits_correctly_with_column_path() {
+    let actual = nu!(
+        cwd: "tests", pipeline(
+        r#"
+            echo [
+                [home, barn];
+
+                ['home/viking/spam.txt', 'barn/cow/moo.png']
+                ['home/viking/eggs.txt', 'barn/goat/cheese.png']
+            ]
+            | path split -c [ home barn ]
+            | get barn
+            | flatten
+            | length
+        "#
+    ));
+
+    assert_eq!(actual.out, "6");
+}