better golden-tests

[maralorn]

• test both modes:
  • [x] nix-build
  • [x] nix build
• test the following circumstances
  • [x] failed job gets marked as failed
  • [x] unfinished job get not marked finished
  • [ ] Make sure errors get logged.
  • [ ] Detect hash mismatches
  • [ ] Detect waiting for lock state