Hello, I work is an ongoing collection of demonstrative messages found on eBay auctions for typewriters, hosted here. The blog showcases the diversity of approaches to demonstrating the machine's functionality.
It's not just "qwertyiop..." collections of sequential letter-mashing, although those are certainly present. Most machines lack the ability to correct mis-typings, so some can be records of struggles with the archaic technology. Many anthropomorphize the machine as an unknown entity in need of help ("I am a typewriter! Take me home!") Rarest are stream-of-consciousness examples made upon discovery of a functioning machine, often with musings about the difference from contemporary technology. But all of them have the near-meta quality of typing for typing's sake, for the intent of communicating the ability to communicate.