getTileSource(props={}) {
        return new OpenSeadragon.TileSource(OpenSeadragon.extend({
            width: 1500,
            height: 1000,
            tileWidth: 200,
            tileHeight: 150,
            tileOverlap: 0
        }, props));
    }
Get mocked tile source
@return {OpenSeadragon.TileSource}