Command tests (#922)

* WIP command tests

* Finish marking todo tests

* update

* update

* Windows cd test ignoring

crates/nu-command/tests/format_conversions/xlsx.rs

@@ -0,0 +1,31 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn from_excel_file_to_table() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            open sample_data.xlsx
+            | get SalesOrders
+            | nth 4
+            | get Column2
+        "#
+    ));
+
+    assert_eq!(actual.out, "Gill");
+}
+
+#[test]
+fn from_excel_file_to_table_select_sheet() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            open sample_data.xlsx --raw
+            | from xlsx -s ["SalesOrders"]
+            | columns
+            | get 0
+        "#
+    ));
+
+    assert_eq!(actual.out, "SalesOrders");
+}