How can I easily run the same tests on different data without duplicating a lot of code? If I follow my usual pattern, I start off with a couple of tests where I write some code then cut-and-paste that a couple of times. I add a few more tests before I realize I have a mess. If I had the foresight to know that I would make a mess (again), I would have started with a table of data and a little bit of code that went through it.
Source: Separate data and behavior with table-driven testing, an article by brian d foy.