Add initial test

crates/nu-cli/tests/commands/headers.rs

@@ -0,0 +1,15 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn headers() {
+    let actual = nu!(
+    cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            open sample_headers.xlsx
+            | get Sheet1
+            | headers
+            | get Column1
+            | from-json"#
+    ));
+    assert_eq!(actual, "r1c1r2c1")
+}