public void TestAddNew()
{
XSSFWorkbook wb = new XSSFWorkbook();
XSSFSheet s = wb.CreateSheet() as XSSFSheet;
Assert.AreEqual(null, wb.GetTheme());
StylesTable styles = wb.GetStylesSource();
Assert.AreEqual(null, styles.GetTheme());
styles.EnsureThemesTable();
Assert.IsNotNull(styles.GetTheme());
Assert.IsNotNull(wb.GetTheme());
wb = XSSFTestDataSamples.WriteOutAndReadBack(wb) as XSSFWorkbook;
styles = wb.GetStylesSource();
Assert.IsNotNull(styles.GetTheme());
Assert.IsNotNull(wb.GetTheme());
}