Legacy is everywhere.From 30-year-old mainframe systems to a startup's one-year-old app that was rushed to market. In the software industry, it is more common to start projects re-building existing systems than building something new.When you work with a legacy system you are faced with many challenges. Releases and testing are slow and costly. There's an ever-growing amount of defects. There are plans from engineering to 'refactor'. Or even to com...