message: docs: adding test debug instructions
diff: @@ -111,6 +111,19 @@ reused in other integration tests. If it's likely be reused, please add the
  appropriate functions to existing utilities or add new test utilities. If it's
  likely a one-off change, it can be scoped to the existing test file.
  +# Debugging integration tests
  +
  +The Envoy integration test framework is generally designed to fast-fail when
  +things go wrong, with an explanatory message such as
  +"Timed out waiting for new connection."
  +but it's not always clear what the underlying cause is. Because there are many
  +Envoy components under test, often the best tool for debugging is to try to get
  +a run of the test with `--test_arg="-l debug"`, or `--test_arg="-l trace"` ideally
  +with a clean run (if it's a code change which caused test breakage) or a comparable
  +test (if it's a new test failing). Looking at the conn_manager_impl.cc
  +logs, router.cc logs, and fake_upstream.cc logs, can often give you a feel for
  +what unexpected event is occurring. If that doesn't help, following the GDB
  +instructions to run the test in a debugger or sprinkling cerrs around are both often helpful.
  # Deflaking tests
  