@Test
public void whenCalculatingPowerSet_thenCorrect() {
final Set<Character> chars = ImmutableSet.of('a', 'b');
final Set<Set<Character>> result = Sets.powerSet(chars);
final Set<Character> empty = ImmutableSet.<Character>builder().build();
final Set<Character> a = ImmutableSet.of('a');
final Set<Character> b = ImmutableSet.of('b');
final Set<Character> aB = ImmutableSet.of('a', 'b');
assertThat(result, contains(empty, a, b, aB));
}
