I found a bit strange result of Combinatorics.power

[t-mochizuki]

Node version is v0.12.4.

I have confirmed following tests.

/*
 * use mocha to test me
 * http://visionmedia.github.com/mocha/
 */
var assert, Combinatorics;
if (this['window'] !== this) {
    assert = require("assert");
    Combinatorics = require('../.');
}
var is_deeply = function (a, e, m) {
    return function () {
        assert.equal(JSON.stringify(a), JSON.stringify(e), m)
    }
};
describe('Combinatorics.power', function () {
    var a = [], c = Combinatorics.power(a);
    it(c, is_deeply(c.toArray(), [
        []
    ]));
    a = 'abc'.split(''), c = Combinatorics.power(a);
    it(a, is_deeply(c.toArray(), [
        [],
        ["a"],
        ["b"],
        ["a", "b"],
        ["c"],
        ["a", "c"],
        ["b", "c"],
        ["a", "b", "c"]
    ]));
    it(0+c, is_deeply(0+c, c.toArray().length));
    it(c.length, is_deeply(c.length, c.toArray().length));
    it(a, is_deeply(c.filter(function(a){return a.length === 2}),
                    Combinatorics.combination(a,2).toArray()
           ));

    a = ["a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9",
         "b0", "b1", "b2", "b3", "b4", "b5", "b6", "b7", "b8", "b9",
         "c0", "c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8", "c9",
         "d0"]
    c = Combinatorics.power(a);
    it(a, is_deeply(c.toArray(), []));

    a = ["a0", "a1", "a2", "a3", "a4", "a5", "a6", "a7", "a8", "a9",
         "b0", "b1", "b2", "b3", "b4", "b5", "b6", "b7", "b8", "b9",
         "c0", "c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8", "c9",
         "d0", "d1"]
    c = Combinatorics.power(a);
    it(a, is_deeply(c.toArray(), [[]]));
});

I added two tests to test/power.js. But, I think that its two tests should not be passed.