Enable installing test CA on Android & add test for it

telemetry/telemetry/internal/platform/platform_backend_unittest.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import logging
 import time
 import unittest
 
 from telemetry.core import platform as platform_module
+from telemetry.testing import tab_test_case
 from telemetry import decorators
 
 
 class PlatformBackendTest(unittest.TestCase):
   @decorators.Disabled('mac',       # crbug.com/440666
                        'vista',     # crbug.com/479337
                        'chromeos',  # crbug.com/483212
                        'win')       # catapult/issues/2282
   def testPowerMonitoringSync(self):
     # Tests that the act of monitoring power doesn't blow up.
@@ skipping 10 matching lines @@
       # pylint: disable=protected-access
       browser_mock._browser_backend = lambda: None
       # Monitor the launcher, which is always present.
       browser_mock._browser_backend.package = 'com.android.launcher'
 
     platform.StartMonitoringPower(browser_mock)
     time.sleep(0.001)
     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())