Quality Code: Software Testing Principles, Practices, and Patterns

Getting Started

Testing an existing piece of software holds a different set of challenges from testing something you are writing, particularly if it is of any size. The Timepicker Addon had just over 2100 lines of code when I started.

You first need to choose where to start. Testable entities—functions in JavaScript—that have few or no dependencies, provide you a way to start with something simpler—a way to get a foothold—and work your way up the chain. The first commit, of course, was just setting up the test framework [72007f6].

I chose to start with a series of top-level private functions within the immediately invoked function expression (IIFE) that wraps every well-written jQuery plugin. But the functions were private, so I had to decide ...