Dirty systems are systems which lack documentation, have few or no defined requirements, have no standardized design or architecture, and have unknown levels of defects. These systems are very difficult to maintain and test due to high complexity and low understanding. People are often afraid to make any changes to this type of software because of the high risk of breaking things that currently work correctly. In many cases, these systems are legacy systems and were never tested well originally. After years of maintenance, these systems often are in disarray due to the lack of control. The...