Explicit testing of this in 2017 and 2018 TurboTax. It's easy to prepare a tax return where all of the income is long-term capital gains (enter only a Form 1099-DIV showing just capital gains distributions) and see that Tax History indicates the income falls in an ordinary income tax bracket. Compare that to the Qualified Dividends and Capital Gain Tax Worksheet which correctly shows that none of the income is taxable as ordinary income.
