test_log: Add test case for exceptions happening in on_start

locust/test/test_log.py

@@ -204,3 +204,33 @@ def my_task(self):
             f"{socket.gethostname()}/INFO/root: custom log message",
             log_content,
         )
+
+    def test_user_broken_on_start(self):
+        with temporary_file(
+            textwrap.dedent(
+                """
+            from locust import HttpUser, task
+            
+            class TestUser(HttpUser):
+                host = "invalidhost"
+
+                def on_start(self):
+                    self.client.get("/")
+                """
+            )
+        ) as file_path:
+            output = subprocess.check_output(
+                [
+                    "locust",
+                    "-f",
+                    file_path,
+                    "-t",
+                    "1",
+                    "--headless",
+                ],
+                stderr=subprocess.STDOUT,
+                timeout=10,
+                text=True,
+            )
+
+        self.assertIn("ERROR/locust.user.users: Invalid URL", output)