> Shouldn't be too hard to write test cases for tax code. I would disagree here -- like timezones, tax software has the disadvantage of being both extremely bo

> Shouldn't be too hard to write test cases for tax code. I would disagree here -- like timezones, tax software has the disadvantage of being both extremely boring, and very fiddly (thus requiring close attention). This combination makes it very hard to maintain the concentration that's required to write exhaustive tests.