Data engineering·Orchestration and running it in anger
before merging the refactor you run the new model over last month and diff its output against what the old one produced.
Golden run
Also calledreference run, known-good output
A retained known-good output used as the comparison baseline when changing transformation logic. It is how you refactor a two-hundred-line model with any confidence, because the test is not 'does it run' but 'is every row the same as before'. Where rows do differ, the useful discipline is that each difference must be explained rather than accepted in bulk.