Testing is about information. We do things to systems in order to get information about the system. From there, we make educated guesses about the systems likely behavior in the future. For example, I might test an installation on a certain hardware configuration, and then from there make statements about the installer's likely behavior on the same hardware configuration at a customer site. Such statements probably take the form, "yup, it'll work", and they can be made explicitly or they can be made implicitly ("Pass").
Testing can be broken down into those two parts:
- doing something and seeing what happens
- predicting future events
If you haven't done something and seen what happens, you haven't tested. If you haven't told someone about it, you haven't tested.
It's easy to get caught up in the doing, but don't forget the communication side of it. Tell someone - in a test plan, in an email, in a green bar in your IDE, in conversation. You're not done until you've told someone.