How should I test a catalogue-wide change before applying it to every product?

Create a representative test set that includes normal products plus edge cases: multiple variants, missing values, unusual characters, different currencies, long text, out-of-stock items and category-specific attributes. Apply the proposed change only to that set, then validate the storefront, search, filters, feeds and any connected marketplaces. Compare values before and after. A catalogue-wide change should be promoted only when the test proves both the intended outcome and the absence of unintended changes in adjacent fields.