Validate dailychart json data

test/test_app.py

@@ -1,6 +1,7 @@
 import pytest
 import json
 import os
+from datetime import datetime
 from puppetboard import app
 from pypuppetdb.types import Node, Report
 from puppetboard import default_settings
@@ -544,5 +545,16 @@ def test_json_daily_reports_chart_ok(client, mocker):
     mocker.patch.object(app.puppetdb, '_query', side_effect=dbquery.get)
 
     rv = client.get('/daily_reports_chart.json')
+    result_json = json.loads(rv.data.decode('utf-8'))
+
+    assert 'result' in result_json
+    assert (len(result_json['result']) ==
+            app.app.config['DAILY_REPORTS_CHART_DAYS'])
+    day_format = '%Y-%m-%d'
+    cur_day = datetime.strptime(result_json['result'][0]['day'], day_format)
+    for day in result_json['result'][1:]:
+        next_day = datetime.strptime(day['day'], day_format)
+        assert cur_day < next_day
+        cur_day = next_day
 
     assert rv.status_code == 200