void setUp() {
    if (emptySetProportion + singletonSetProportion > 1.01) {
      throw new SkipThisScenarioException();
    }

    Random rng = new Random();
    for (int i = 0; i < 0x1000; i++) {
      double setSize = rng.nextDouble();
      if (setSize < emptySetProportion) {
        sets[i] = ImmutableSet.of();
      } else if (setSize < emptySetProportion + singletonSetProportion) {
        sets[i] = ImmutableSet.of(PRESENT);