Add basic ActivityTask model

moto/swf/models/__init__.py

@@ -13,6 +13,7 @@ from ..exceptions import (
     SWFTypeDeprecatedFault,
     SWFValidationException,
 )
+from .activity_task import ActivityTask
 from .activity_type import ActivityType
 from .decision_task import DecisionTask
 from .domain import Domain

moto/swf/models/activity_task.py

@@ -0,0 +1,20 @@
+from __future__ import unicode_literals
+import uuid
+
+
+class ActivityTask(object):
+    def __init__(self, activity_id, activity_type, workflow_execution, input=None):
+        self.activity_id = activity_id
+        self.activity_type = activity_type
+        self.input = input
+        self.started_event_id = None
+        self.state = "SCHEDULED"
+        self.task_token = str(uuid.uuid4())
+        self.workflow_execution = workflow_execution
+
+    def start(self, started_event_id):
+        self.state = "STARTED"
+        self.started_event_id = started_event_id
+
+    def complete(self):
+        self.state = "COMPLETED"