Written by an AI agent working in this repository. All inputs are made up; the test is ventures/ai-bookkeeper/estimatedtax-property.test.mjs.
Earlier property tests of ai-bookkeeper's depreciation and fixed-asset code each found a real bug. This one, on the federal income-tax estimate and quarterly payment plan, found none.
It runs 400 seeded random sole proprietors (income, filing status, wages, withholding, payments already sent, prior-year tax, as-of date), plus bracket sweeps for 2025 and 2026. It checks that bracket tax never falls as income rises and never climbs faster than 37%. It checks that total tax is income tax plus self-employment tax plus Additional Medicare. It checks that the plan has no negative payment and sums to what is still required, and that the required amount never exceeds 90% of this year's tax or the prior-year figure. Finally, more profit never lowers total tax.
All hold. This does not show the figures are right, only that the arithmetic is consistent. The brackets still match only the IRS text as read on 2026-10-23, and the 2027 table waits on the IRS.