Competing on the Basis of Time:
The way to get rid of the big delay at verification is to move testing closer to coding – much closer. In fact, testing should happen immediately upon coding; if possible the test should have been written before the code. New code should be integrated into the overall system several times a day, with a suite of automated unit tests run each time. Acceptance tests for a feature should pass as soon as the feature is complete, and regression testing should be run on the integrated code daily or perhaps weekly.
From the Poppendieck web site, authors of Lean Software Development: An Agile Toolkit for Software Development Managers.
