You can, but if there were critical bugs fixed between the test version and the final, it could screw your saves permanently (unless you went in and edited them to fix the issue). The safest thing to do, is just keep a back up between official versions. Those are the only ones Tinkerer can semi-guarantee will be fine. And even then, as game testers will tell you, there is no bullet-proofing code.So far I've never downloaded the test version but I'm curious so I will anyways. I can just transfer my future saves of this test version to the versions we'll get in the future, right?
For what it's worth, I've carried saves from test versions to official and never had noticeable issue. But I've stayed up to date with the game, and never really had to worry about anything before new content functioning.