Stuart Herbert has his latest post in his "PHP Components" series on his blog today - a recommendation to include unit tests along with the release of you component.
I'm now going under the bonnet of our components, and looking at the different file roles that the PEAR installer expects to find when we distribute our component as a PEAR-compatible package. One of the most important file roles allows you to ship your tests with your package - and it's vital that this is something that you get in the habit of doing routinely.
He recommends "testing your code and shipping your tests" along with the component(s) you're releasing. Not only does it help you create a better quality end result but also makes it simpler for other developers to make changes and know they're not breaking things. He describes unit tests for those not familiar and includes a specific example of the CommandLineLibrary and its related tests.