Merge pull request #2713 from locustio/Give-better-error-message-if-U…

…ser-subclass-doesnt-call-base-constructor

Give better error message if User subclass doesnt call base constructor

locust/runners.py

@@ -223,6 +223,9 @@ def spawn(user_class: str, spawn_count: int) -> list[User]:
             new_users: list[User] = []
             while n < spawn_count:
                 new_user = self.user_classes_by_name[user_class](self.environment)
+                assert hasattr(
+                    new_user, "environment"
+                ), f"Attribute 'environment' is missing on user {user_class}. Perhaps you defined your own __init__ and forgot to call the base constructor? (super().__init__(*args, **kwargs))"
                 new_user.start(self.user_greenlets)
                 new_users.append(new_user)
                 n += 1

locust/test/test_runners.py

@@ -144,6 +144,24 @@ def reset_state(self):
 
 
 class TestLocustRunner(LocustRunnerTestCase):
+    def test_missing_constructor_call_in_user(self):
+        class BadUser(User):
+            def __init__(self, *args, **kwargs):
+                pass  # not calling base class constructor!!!
+
+            @task
+            def t(self):
+                pass
+
+        environment = Environment(user_classes=[BadUser])
+        runner = LocalRunner(environment)
+        with self.assertRaises(AssertionError) as assert_raises_context:
+            runner.spawn_users({BadUser.__name__: 1})
+        self.assertIn(
+            "Attribute 'environment' is missing on user BadUser. Perhaps you defined your own __init__ and forgot to call the base constructor",
+            str(assert_raises_context.exception),
+        )
+
     def test_cpu_warning(self):
         _monitor_interval = runners.CPU_MONITOR_INTERVAL
         runners.CPU_MONITOR_INTERVAL = 2.0