I Rejected My Reference Tools' Assumptions, Then Inherited One
I built a loan calculator because the ones I was using assumed something wrong about how a borrowing decision happens. I caught that assumption early and designed against it. Then I built extra-payment handling, tested it, and considered it done. It took running the same input through a second market's convention to see that I'd inherited a different assumption from the same tools — and encoded…
The author built a loan calculator to address inaccuracies in existing ones. They discovered an assumption that the calculators made, which was that users wouldn't reopen the tool after initial use. This assumption led to the design of calculators that couldn't save or compare multiple loan scenarios. The author realized they needed a calculator that could handle multiple scenarios and save the input conditions.
They found that their previous tool inherited the same assumption, resulting in a different approach to calculating loan prepayment. The author redesigned their calculator to accommodate both scenarios: shortening the term or reducing the payment. They also added a setting to specify the prepayment mode, which helped them accurately calculate the interest saved and months saved.
The author learned the importance of understanding the assumptions behind tools and designing them to fit the specific needs of users.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
