If all you are wanting to do is "test" equipment then you will need these things.
12 volt power supply. Radio Shack has one that is 15 amps and is about $100. You might find a larger one but they really start getting expensive as you go up in amperage. Our 200 amp power supplies for our soundrooms are about $1500.
A headunit and at least one pair of speakers.
Make "jacks" for the RCA inputs of the deck & speakers. Usually use a spring terminal from a pre-fab box for the speaker inputs. Use some female RCA connectors for the input of the deck.
Have spring clipped wires for your power, ground and remote turn-on. These will come directly from you power supply.
Incorporate a "switch" so that you can switch from the decks internal power to a amp ( so that you can "test" a amp" with your speakers on the bench)
That's about it.. not too difficult if you understand the way car audio is wired.