Fictional teaching inputs. Keep originals, reference answers and actual tool outputs separate.

Load departments.csv in spreadsheet batch tools, keep all three columns, no deduplication. Generate a four-row preview and split on Department. Inspect manifest.csv and its three data files. Reassemble only those data files, never the manifest. Check row count 4, four unique IDs and original ID-to-group membership. bad-reassembled.csv deliberately retains 4 rows but repeats 0001 and loses 0004. Reject it and rebuild from original source rather than deleting duplicates to conceal the loss.
