Can I test my own network?

There is nothing hindering you from testing within your own network. To get a rudimentary understanding of what is involved with testing, I suggest you familiarize yourself with the Penetration Testing Execution Standard, OSSTMM, and other similar pentesting frameworks. Once you begin establishing the who, what, when, where and why, it will make things easier for you to set up your own environment. For testing I never set up anything in my network (there is no trying to mimic a client) because I can never know what patch levels they have, what software is installed, and so forth. Rather than re-invent wheels, there are plenty of "hackable" virtualized instances you could download. I suggest NetInVM. But to answer your question, what you do in your private network is not bound by any of the common USC (US law) computer related laws.