Actually, in my experience "sanity checks" were very often built into financial models. Does your balance sheet balance? That's a pretty basic "unit test". Do

Actually, in my experience "sanity checks" were very often built into financial models. Does your balance sheet balance? That's a pretty basic "unit test". Do your calculated values match the financial statements values? No? Throw an error. Divide by zero? Reference a blank cell (similar to an unset variable)? Using a value as a number? Referencing outside of a range? All immediately throw an error that will flow through your model. And code review often does take place - in banking at least, models written by analysts are checked by associates and then VPs. People who understand what the numbers should look like can spot mistakes pretty quickly using a TI calculator. Source control is a problem, but many models are one-offs for specific projects - no company (or deal) is structured identically. You're identifying problems that have, for the most part, already been solved. Not perfectly, but in ways that work well within the structures that have been built around the use of Excel as a core tool.