assertTrue(isOneOrFive.apply(1));
    assertTrue(isOneOrFive.apply(5));
    assertFalse(isOneOrFive.apply(3));
    assertFalse(isOneOrFive.apply(null));
  }

  public void testIn_equality() {
    Collection<Integer> nums = ImmutableSet.of(1, 5);
    Collection<Integer> sameOrder = ImmutableSet.of(1, 5);
    Collection<Integer> differentOrder = ImmutableSet.of(5, 1);