static void compareStyleSheets(const SheetVector& oldStyleSheets, const SheetVector& newStyleSheets, const ContentsVector& expAddedSheets, UpdateType testUpdateType)
 {
     ContentsVector addedSheets;
     UpdateType updateType = static_cast<UpdateType>(TreeScopeStyleSheetCollection::compareStyleSheets(oldStyleSheets, newStyleSheets, addedSheets));
     EXPECT_EQ(testUpdateType, updateType);
     EXPECT_EQ(expAddedSheets.size(), addedSheets.size());
     if (expAddedSheets.size() == addedSheets.size()) {
         for (unsigned i = 0; i < addedSheets.size(); i++)
             EXPECT_EQ(expAddedSheets.at(i), addedSheets.at(i));
     }
 }