getTiledImage(viewer=null, props={}) {
        viewer = viewer || this.getViewer();
        return OpenSeadragon.extend({
            viewer: viewer,
            source: OpenSeadragon.TileSource.prototype,
            redraw: function() {},
            _tileCache: viewer.tileCache
        }, props);
    }
Get mocked tiled image: it has not all props that might be required. If your
tests fails because they do not find some props on a tiled image, add them here.

Requires viewer reference (mock or real). Automatically created if not provided.
@return {OpenSeadragon.TiledImage}