Think of rabbits, and you're likely to think of the phrase "breeding like rabbits." The Rabbit test has a number of variants, but they all work pretty much the same way. The basic Rabbit gets one free Drudge Rabbit (1/1 colorless regenerating creature) every turn. Drudge Rabbits regenerate whenever necessary, for no cost. The Rabbit will attack whenever she can do so, but will always try to leave enough Drudges untapped to block all of your blockable creatures. Other than that, the Rabbit follows the Goldfish rules.

Other variants of the basic Rabbit test replace the Drudge Rabbits with either Will-O'-Rabbits (0/1 colorless regenerating fliers--these never attack, for obvious reasons), Scryb Rabbits (1/1 colorless fliers), or Rabbit Thallids (1/1 green creature). All of the Rabbit tests give a crude measurement of how well your deck will do against a "weenie" or "horde" deck. For an extra challenge, give the Rabbit a Meekstone and/or a Winter Orb, since many weenie decks make use of these cards.

Tom Pitt of CompuServe uses a very tough Rabbit variant called the Rat test. The Rat opponent gets one free Plague Rat each turn, and always attacks with half of her rats (rounding down) whenever able to do so. The rest of the rats will block in whatever way is most effective. If you attack with any flying creatures, then half (rounded up) of the untapped rats gain flying until the end of the turn. If you play a CoP: Black, it lasts for only three turns and is then destroyed.

Another variant on the Rabbit test, suggested by Izzy Gambliel of Metro Seattle Gamers, is the Angel test. The Angel opponent does nothing for the first four turns, but then gets one free Serra Angel (4/4 white flier, attacking doesn't cause it to tap) every turn. She attacks whenever she has a chance of dealing damage to you or killing one of your creatures, and blocks whenever possible. This simulates decks which take a while to get rolling, but pump out large creatures as soon as they have sufficient mana.