I have a generated dataset that creates over 2 million rows of data for a unit test (something with security that needs thorough testing). I noticed that adding these rows with QTest::newRow slows down the more you add and it turns out that the rows are stored in a rather naive linked list implementation.
Every append goes through the whole list to find the last element...

If someone could change this so it prepends rows instead of appending them, newRow could be done in a constant time.