Dice Exercise in Ruby

This was a coding exercise given to me by a prospective employer. It specified that it should be done in an object oriented language. That rules out JavaScript. While you can write object-oriented JS, it's hard to imagine anyone arguing that it's an object oriented language a la Java, C++, and C#, which were specifically mentioned in the exercise prompt as language options. I know Ruby slightly better than I know those three, so I chose Ruby.

The prompt

1. Build an application that rolls a six-sided die to obtain a random value between 1 and 6.
2. Introduce the concept of a cup so that multiple dice can be rolled at one time.
3. Create a loaded die that, given a predetermined number, will land on that number 50% of the time (we can't be too obvious with our loaded die).

The output should look similar to this:

Rolling 1 die: 4
Rolling 2 dice in a cup: 8
Rolling 6 dice in a cup: 23
Rolling 12 dice in a cup: 41
Rolling 120 dice in a cup: 415
Rolling a loaded die set to '1': 1
Rolling a loaded die set to '1': 3

Notes from the reviewer

• Everything is in one file, when it should be one class per file or almost one class per file.
• Code is squashed together and should be formatted better.
• Testing occurs inline, but should use Test::Unit or rspec.
• Can't add loaded dice to cup.
• Comments acknowledge that loaded die hit set number more than 50% of the time. Try to fix it.