class SwingTree extends AbstractSwingContainer implements XulTree {

  public XulTreeCols getColumns() {
    return this.columns;
  }

}

class SwingTreeTest {

   XulRunner runner;
   XulDomContainer container;
   XulTree tree;
   XulTree tree2;
   XulTree tree3;
   Document document;

  @Test
  public void testGetCols() throws Exception {

    assertEquals( tree.getColumns(), document.getElementById( "column_list" ) );
  }

}