> Supporting the old software engineering folklore that the earlier a bug is introduced (and the later it is found) the harder and more expensive it is to fix.

I wouldn't call it folklore as there are numerous studies supporting it.

EDIT: I decided to crack open Code Complete for anyone who is interested [1].

[1] "Researchers at Hewlett-Packard, IBM, Hughes Aircraft, TRW and other organizations have found that purging an error by the beginning of construction allows rework to be done 10 to 100 times less expensively than when it's done in the last part of the process, during system test or after release (Fagan 1976; Humphrey, Snyder, and Willis 1991; Willis et al. 1998; Grady 1999; Shull et al. 2002; Boehm and Turner 2004)".