test.js

        var scheme = new PyramidScheme({
            minzoom: 0,
            maxzoom: 2,
            concurrency: 1,
            metatile: 1
        });

        var tiles = [];
        scheme.task = {
            render: function(tile) {
                tiles.push(tile.toString());
                scheme.unique(tile);
            },
            finished: function() {
                assert.deepEqual(tiles, [ '0/0/0', '1/0/0', '2/0/0', '2/1/0', '2/0/1',
                    '2/1/1', '1/1/0', '2/2/0', '2/3/0', '2/2/1', '2/3/1', '1/0/1', '2/0/2',
                    '2/1/2', '2/0/3', '2/1/3', '1/1/1', '2/2/2', '2/3/2', '2/2/3', '2/3/3' ]);
                done();
            }
        };

        scheme.start()