That's exactly what I did to learn River — implementing simple apps and testing their execution with pgtestdb: https://github.com/lukasschwab/river-playground
The starter skeleton was LLM-generated and not quite perfect, but discovering the coding agent's mistakes was satisfying in its own right.
I'm both surprised and excited to hear that pgtestdb, out of the box, can give anyone a ~nearly as fast experience.
Going to have to throw some tokens at pooling... very interesting idea.
Thank you, Brandur!