Add tests for headers command

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

@@ -1,7 +1,22 @@
 use nu_test_support::{nu, pipeline};
 
 #[test]
-fn headers() {
+fn headers_uses_first_row_as_header() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+            r#"
+            open sample_headers.xlsx
+            | get Sheet1
+            | headers
+            | get header0
+            | from-json"#
+        ));
+
+    assert_eq!(actual, "r1c0r2c0")
+}
+
+#[test]
+fn headers_adds_missing_column_name() {
     let actual = nu!(
     cwd: "tests/fixtures/formats", pipeline(
         r#"
@@ -11,5 +26,6 @@ fn headers() {
             | get Column1
             | from-json"#
     ));
+
     assert_eq!(actual, "r1c1r2c1")
 }

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

@@ -10,6 +10,7 @@ mod first;
 mod format;
 mod get;
 mod group_by;
+mod headers;
 mod histogram;
 mod insert;
 mod last;