Merge pull request #1287 from locustio/generate-more-descriptive-erro…

…r-when-user-forgot-do-define-tasks

Give a more descriptive error when the Locust or TaskSet has no tasks.

locust/core.py

@@ -465,6 +465,8 @@ def schedule_task(self, task_callable, args=None, kwargs=None, first=False):
             self._task_queue.append(task)
 
     def get_next_task(self):
+        if not self.tasks:
+            raise Exception("No tasks defined. use the @task decorator or set the tasks property of the TaskSet")
         return random.choice(self.tasks)
 
     def wait_time(self):

locust/test/test_locust_class.py

@@ -31,6 +31,20 @@ class MyTasks(TaskSet):
         self.assertEqual(t1_count, 5)
         self.assertEqual(t2_count, 2)
 
+    def test_tasks_missing_gives_user_friendly_exception(self):
+        class User(Locust):
+            wait_time = constant(0)
+            tasks = None
+            _catch_exceptions = False
+
+        class MyTasks(TaskSet):
+            tasks = None
+
+        l = MyTasks(User(self.environment))
+        self.assertRaisesRegex(Exception, "No tasks defined.*", l.run)
+        l.tasks = None
+        self.assertRaisesRegex(Exception, "No tasks defined.*", l.run)
+
     def test_task_decorator_ratio(self):
         t1 = lambda l: None
         t2 = lambda l: None
@@ -178,6 +192,7 @@ def t1(self):
         taskset = MyTaskSet3(self.locust)
         self.assertEqual(len(taskset.tasks), 3)
 
+
     def test_wait_function(self):
         class MyTaskSet(TaskSet):
             a = 1