The Penny Gap
A shop’s invoice preview is occasionally a few cents lower than the prices on its product cards. Increasing the quantity makes the difference grow. Other products total correctly, and the same discrepancy appears in saved invoices.
The bug report
You get the whole project — a React front end, an Express API, and Mongoose models — opened in a browser editor. Reproduce the symptom by reading the code, change what’s wrong, and run the hidden tests to prove it.
What the fix must prove
- quotes whole-dollar products correctly
- preserves every cent across fractional prices and quantities
- stores the invoice amount returned to the customer
- rejects invalid quantities without creating invoices
- returns a clear error for an unavailable product