zmq: add test for zmq start up failure when port already in use

src/ert/ensemble_evaluator/evaluator.py

@@ -436,9 +436,8 @@ def log_exception(task_exception: BaseException, task_name: str) -> None:
         )
 
     async def run_and_get_successful_realizations(self) -> list[int]:
-        await self._start_running()
-
         try:
+            await self._start_running()
             await self._monitor_and_handle_tasks()
         finally:
             self._server_done.set()

tests/ert/unit_tests/ensemble_evaluator/test_ensemble_evaluator.py

@@ -5,6 +5,7 @@
 from unittest.mock import patch
 
 import pytest
+import zmq.asyncio
 from hypothesis import given
 from hypothesis import strategies as st
 from pydantic import ValidationError
@@ -97,6 +98,19 @@ async def test_evaluator_handles_dispatchers_connected(
     assert evaluator._dispatchers_empty.is_set()
 
 
+async def test_evaluator_raises_on_fail_start(make_ee_config):
+    ee_config = make_ee_config(use_ipc_protocol=False)
+    ctx = zmq.asyncio.Context()
+    socket = ctx.socket(zmq.ROUTER)
+    try:
+        socket.bind(f"tcp://*:{ee_config.router_port}")
+        evaluator = EnsembleEvaluator(TestEnsemble(0, 2, 2, id_="0"), ee_config)
+        with pytest.raises(RuntimeError, match="Address already in use"):
+            await evaluator.run_and_get_successful_realizations()
+    finally:
+        ctx.destroy()
+
+
 async def test_no_config_raises_valueerror_when_running():
     evaluator = EnsembleEvaluator(TestEnsemble(0, 2, 2, id_="0"), None)
     with pytest.raises(ValueError, match="no config for evaluator"):