Slide s2 = ppt.getSlides()[1];
assertEquals(257, s2._getSheetNumber());
assertEquals(6, s2._getSheetRefId());
// Add another slide, goes in at the end
Slide s3 = ppt.createSlide();
assertTrue(ppt.getSlides().length == 3);
assertEquals(258, s3._getSheetNumber());
assertEquals(8, s3._getSheetRefId());