You can test how the fishtest worker works using a free 2 cores instance for max 6 hours on Google Colaboratory:

• Signup for a free account
• Create a new notebook
• Paste this text writing your fishtest username/password:

  !git clone --depth=1 --single-branch --branch master https://github.com/official-stockfish/fishtest.git
  !python3 fishtest/worker/worker.py <username> <password> --concurrency MAX --max_memory MAX

• Start the notebook
• You can save the notebook on your Google Drive