How to delete all rows from QTableWidget

Just set the row count to 0 with:

mTestTable->setRowCount(0);

it will delete the QTableWidgetItems automatically, by calling removeRows as you can see in QTableWidget internal model code:

void QTableModel::setRowCount(int rows)
{
    int rc = verticalHeaderItems.count();
    if (rows < 0 || rc == rows)
        return;
    if (rc < rows)
        insertRows(qMax(rc, 0), rows - rc);
    else
        removeRows(qMax(rows, 0), rc - rows);
}