Make test_net_info a bit more robust.

infra/services/sysmon/test/system_metrics_test.py

Index: infra/services/sysmon/test/system_metrics_test.py
diff --git a/infra/services/sysmon/test/system_metrics_test.py b/infra/services/sysmon/test/system_metrics_test.py
index 65ae0127bfd579eedf0950e4ec7daca0b01b0b57..315663f52627727acc2f815dd00deb2ca0151c51 100644
--- a/infra/services/sysmon/test/system_metrics_test.py
+++ b/infra/services/sysmon/test/system_metrics_test.py
@@ -111,19 +111,27 @@ class SystemMetricsTest(unittest.TestCase):
     self.assertIsNotNone(total)
     self.assertLessEqual(free, total)
 
-  # See http://crbug.com/624369
-  def DISABLED_test_net_info(self):  # pragma: no cover
+  def test_net_info(self):  # pragma: no cover

[Sergey Berezin, 2016/06/30 19:14:04]

Remove the pragma - here and in system_metrics.py.

[dsansome, 2016/07/01 00:17:54]

Oops thanks

     system_metrics.get_net_info()

[Sergey Berezin, 2016/06/30 19:14:04]

It worries me that we have to depend on the actual system network setup in this
test, and thus, have an inherent source of nondeterminism. OTOH, I can't think
of a better way to test that we got the keys correctly out of
psutil.net_io_counters. But short of that, I'd just mock it out.

[dsansome, 2016/07/01 00:17:54]

I think I mocked it originally but pgervais hates mocks :(

 
+    interface_names = [fields[0][1]
+                       for fields, _
+                       in system_metrics.net_up.get_all()]
+    self.assertGreater(len(interface_names), 0)
+
     # A network interface that should always be present.
     if sys.platform == 'win32':  # pragma: no cover
-      interface = 'Local Area Connection'
+      self.assertTrue(
+          any(x.startswith('Local Area Connection') for x in interface_names),

[Sergey Berezin, 2016/06/30 19:14:04]

Do we even need these platform-specific asserts? In the end, we are still
checking whatever happens to be the first interface for metrics. Maybe just
check that we have at least one interface?

[dsansome, 2016/07/01 00:17:54]

I wanted to check the field values are actually interface names.  If we screwed
that up, or maybe set fields={'interface': ''} or something, we wouldn't notice
without this check.

+          interface_names)
     elif sys.platform == 'darwin':  # pragma: no cover
-      interface = 'en0'
+      self.assertTrue(
+          any(x.startswith('en') for x in interface_names),
+          interface_names)
     else:  # pragma: no cover
-      interface = 'lo'
+      self.assertIn('lo', interface_names)
 
-    labels = {'interface': interface}
+    labels = {'interface': interface_names[0]}
 
     self.assertIsNotNone(system_metrics.net_up.get(labels))
     self.assertIsNotNone(system_metrics.net_down.get(labels))