I think that first of all you have to list the features that you wish to test and what you are actually going to demonstrate. You said originally that you were just going to test the voice recognition part.
For example, are you going to have a real door with a lock mechanism and microphone and loudspeaker or display etc. with independent power supply. Or are you going to have a simple test system on a breadboard which is capable of recognising a voice passcode and writing a pass/fail message to the serial console ?