Add test to check with notificationhistory but no notification

tests/app/template_statistics/test_rest.py

@@ -5,7 +5,12 @@ import pytest
 from freezegun import freeze_time
 
 from tests import create_authorization_header
-from tests.app.conftest import (sample_template as create_sample_template, sample_notification, sample_email_template)
+from tests.app.conftest import (
+    sample_template as create_sample_template,
+    sample_notification,
+    sample_notification_history,
+    sample_email_template
+)
 
 
 def test_get_all_template_statistics_with_bad_arg_returns_400(client, sample_service):
@@ -223,7 +228,7 @@ def test_get_template_statistics_for_template_returns_empty_if_no_statistics(
 
     assert response.status_code == 200
     json_resp = json.loads(response.get_data(as_text=True))
-    assert json_resp['data'] == {}
+    assert not json_resp['data']
 
 
 def test_get_template_statistics_raises_error_for_nonexistent_template(
@@ -242,3 +247,23 @@ def test_get_template_statistics_raises_error_for_nonexistent_template(
     json_resp = json.loads(response.get_data(as_text=True))
     assert json_resp['message'] == 'No result found'
     assert json_resp['result'] == 'error'
+
+
+def test_get_template_statistics_by_id_returns_empty_for_old_notification(
+    notify_db,
+    notify_db_session,
+    client,
+    sample_template
+):
+    sample_notification_history(notify_db, notify_db_session, sample_template)
+
+    auth_header = create_authorization_header()
+
+    response = client.get(
+        '/service/{}/template-statistics/{}'.format(sample_template.service.id, sample_template.id),
+        headers=[('Content-Type', 'application/json'), auth_header],
+    )
+
+    assert response.status_code == 200
+    json_resp = json.loads(response.get_data(as_text=True))['data']
+    assert not json_resp