Cancel broadcast via API

When a service sends us an XML CAP broadcast message with Cancel
status, and that broadcast is in broadcasting state, we cancel it.

tests/app/v2/broadcast/test_post_broadcast.py

@@ -155,8 +155,54 @@ def test_valid_cancel_broadcast_request_rejects_unapproved_alert_and_returns_201
     assert response_json_for_reject['updated_at'] is not None
 
 
-def test_valid_cancel_broadcast_request_cancels_active_alert_and_returns_201():
-    pass
+def test_valid_cancel_broadcast_request_cancels_active_alert_and_returns_201(
+    client,
+    sample_broadcast_service,
+    notify_db,
+    notify_db_session,
+    mocker
+):
+    auth_header = create_service_authorization_header(service_id=sample_broadcast_service.id)
+
+    # create a broadcast
+    response_for_create = client.post(
+        path='/v2/broadcast',
+        data=sample_cap_xml_documents.WAINFLEET,
+        headers=[('Content-Type', 'application/cap+xml'), auth_header],
+    )
+    assert response_for_create.status_code == 201
+
+    response_json_for_create = json.loads(response_for_create.get_data(as_text=True))
+
+    assert response_json_for_create['cancelled_at'] is None
+    assert response_json_for_create['cancelled_by_id'] is None
+    assert response_json_for_create['reference'] == '50385fcb0ab7aa447bbd46d848ce8466E'
+    assert response_json_for_create['status'] == 'pending-approval'
+
+    # approve broadcast
+    broadcast_message = dao_get_broadcast_message_by_id_and_service_id(
+        response_json_for_create["id"], response_json_for_create["service_id"]
+    )
+    broadcast_message.status = 'broadcasting'
+
+    # cancel broadcast
+    mock_task = mocker.patch('app.celery.broadcast_message_tasks.send_broadcast_event.apply_async')
+
+    response_for_cancel = client.post(
+        path='/v2/broadcast',
+        data=sample_cap_xml_documents.WAINFLEET_CANCEL,
+        headers=[('Content-Type', 'application/cap+xml'), auth_header],
+    )
+    assert response_for_cancel.status_code == 201
+
+    assert len(broadcast_message.events) == 1
+    alert_event = broadcast_message.events[0]
+    mock_task.assert_called_once_with(kwargs={'broadcast_event_id': str(alert_event.id)}, queue='broadcast-tasks')
+
+    assert broadcast_message.status == 'cancelled'
+    assert broadcast_message.cancelled_at is not None
+    assert broadcast_message.cancelled_by_id is None  # broadcast cancelled via API, so not by any single user
+    assert broadcast_message.updated_at is not None
 
 
 def test_cancel_request_does_not_cancel_broadcast_if_reference_does_not_match():