When to consider a story done?

Hi,

We run a 2-week sprint. In the current sprint, that ends on 19th July 2019, we have the stories developed however the tester is occupied with other work which is also prioritized (testing of stories of the previous sprint, there were a couple of production issues hence the delay).

Now the team says, lets mark the stories done if they are developed and if PO okays the demo session in order to avoid spillover. Is it ok to mark the stories done if the stories are not tested by a QA yet.