Requirements for entering Poland by Train? (American, via Berlin)

I am planning on taking a train from Berlin to Krakow in a week or so. I saw in a video online (on YouTube) that Poland has strict entry requirements requiring a recent negative covid test to enter via train. However, the video is 5 years old and I can’t find other info on this. Can anyone possibly let me know if traveling into Poland by train from Germany would have any requirements other than a ticket and a passport! Thank you!