Set up your base robot so that you can let it loose and it will wander around, backing up and/or turning around when it hits obstacles.
This includes: picking out sensors, soldering up sensors, mounting sensors to legos in some way, mounting the sensors to your robot, picking where to put sensors so that your robot won't get stuck, and programming the robot.
Test your robot by letting it wander around in the hallways. One thing to check is to make sure it can escape a corner (if it is driving straight towards an inside corner).
Another thing to test is that if two wandering robots collide, they both "escape" and do not fall apart.