Enable installing test CA on Android & add test for it

telemetry/telemetry/internal/platform/platform_backend_unittest.py

Index: telemetry/telemetry/internal/platform/platform_backend_unittest.py
diff --git a/telemetry/telemetry/internal/platform/platform_backend_unittest.py b/telemetry/telemetry/internal/platform/platform_backend_unittest.py
index b2d3b832bc30ad079f18dad6ba687bad6497368f..b710ea7778ebc1a377955fe291fcf35ea4b49c7f 100644
--- a/telemetry/telemetry/internal/platform/platform_backend_unittest.py
+++ b/telemetry/telemetry/internal/platform/platform_backend_unittest.py
@@ -7,6 +7,7 @@ import time
 import unittest
 
 from telemetry.core import platform as platform_module
+from telemetry.testing import tab_test_case
 from telemetry import decorators
 
 
@@ -37,3 +38,35 @@ class PlatformBackendTest(unittest.TestCase):
     output = platform.StopMonitoringPower()
     self.assertTrue(output.has_key('energy_consumption_mwh'))
     self.assertTrue(output.has_key('identifier'))
+
+
+class PlatformBackendIntegrationTest(tab_test_case.TabTestCase):
+
+  def setUp(self):
+    super(PlatformBackendIntegrationTest, self).setUp()
+    self._platform_backend = self._platform._platform_backend
+
+  def _GetRootCertificates(self):
+    if self._platform_backend.GetOSName() == 'android':
+      return set(self._platform_backend._device.ListDirectory(
+          '/system/etc/security/cacerts/', as_root=True))
+    else:
+      raise NotImplementedError()
+
+  # TODO(nedn): also run this test on linux (crbug.com/756989)
+  @decorators.Enabled('android')
+  def testCAInstallation(self):
+    self.assertTrue(self._platform_backend.supports_test_ca)
+    current_certificates = self._GetRootCertificates()
+
+    # Assert that we have +1 certificate on the system after invoking
+    # InstallTestCa().
+    self._platform_backend.InstallTestCa()
+    self.assertEquals(
+        len(current_certificates) + 1,
+        len(self._GetRootCertificates()))
+
+    # Assert that the system's test certificates should be the same as before
+    # after invoking RemoveTestCa().
+    self._platform_backend.RemoveTestCa()
+    self.assertEquals(current_certificates, self._GetRootCertificates())