Problems found with the test-suite

[maralorn]

The testsuite should:

• assert that only expected errors were emitted.
  • nix errors (NOMState.nixErrors)
  • nom errors, currently just printed to log
• assert that the exit code of nix was expected.
• live stream the nix build output instead of only running the test when nix exited.
• use container tests instead of vm tests.
• should be written in tasty.
• should cover more cases.
• should use the words, golden, property, unit and integration tests each with their correct meaning (or not when we don’t have such tests.)