The software we’ve written has gotten progressively bigger and somewhat more complex. When that happens, it becomes rather tedious to start an Erlang shell, type things in, look at results, and make sure things work after code has been changed. As time passes, it becomes simpler for everyone to run tests that are prepared and ready in advance, rather than following lists of stuff to check by hand all the time. It’s also possible that you’re a fan of test-driven development and so will find tests useful.
When we created an RPN calculator in Chapter 8, we wrote a few tests manually. They were simply a set of pattern matches of the form
Expression that would crash if something went wrong and succeed otherwise. ...