assertThat(sorter.getSelectedColumn(), nullValue());
TreeColumn column = new TreeColumn(sorter.getViewer().getTree(), SWT.NONE);
Event event = new Event();
event.widget = column;
SelectionEvent selectionEvent = new SelectionEvent(event);
sorter.widgetSelected(selectionEvent);
Tree tree = sorter.getViewer().getTree();
assertThat(tree.getSortColumn(), is(column));
assertThat(tree.getSortDirection(), is(SWT.UP));