test: add format filesize kilobytes test

src/builtins/ls.rs

@@ -112,4 +112,9 @@ mod tests {
     fn test_format_filesize_bytes() {
         assert_eq!(format_filesize(6969), "6969B");
     }
+
+    #[test]
+    fn test_format_filesize_kilobytes() {
+        assert_eq!(format_filesize(69420), "69KB");
+    }
 }