Now, granted, I'm sure I could just play through a circuit to make sure everything is working fine, but damnit, I'm a nerd, and I need a function generator and an oscilloscope.
Can these be had for <$100 prices?
you can build signal injectors on the dirt-cheap.
As for scopes, I don't know. My Scope is a tube-powered ordeal from the 60s that was my dad's.