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https://hackernoon.com/my-tests-fail-if-anyone-types-a-dollar-amount-by-hand.
A one-line Vitest rule bans hand-typed prices in MDX; components and build-time SVG charts pull every number from one function.
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I run a concrete cost calculator whose data refreshes monthly, so any price typed into an article goes stale. My rule: no dollar sign followed by a digit anywhere in prose. A Vitest test enforces it, MDX components put computed numbers inside sentences, and one pure function feeds the table, a zero-JS SVG chart and its alt text. Tests also pin the direction of each claim the prose makes.