expected.add(ImmutableSet.of(1, 2, 3));

    Set<Set<Integer>> almostPowerSet = newHashSet(expected);
    almostPowerSet.remove(ImmutableSet.of(1, 2, 3));
    almostPowerSet.add(ImmutableSet.of(1, 2, 4));

    new EqualsTester()
        .addEqualityGroup(expected, powerSet)
        .addEqualityGroup(ImmutableSet.of(1, 2, 3))
        .addEqualityGroup(almostPowerSet)
        .testEquals();