[android] Fail if all devices drop offline while running tests.

build/android/pylib/base/test_dispatcher_unittest.py

 # Copyright 2013 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.
 
 """Unittests for test_dispatcher.py."""
 
 import os
 import sys
 import unittest
 
@@ skipping 168 matching lines @@
     self.assertEqual(len(results.GetPass()), 0)
     self.assertEqual(len(results.GetFail()), 3)
     self.assertEqual(exit_code, constants.ERROR_EXIT_CODE)
 
   def testNoTests(self):
     results, exit_code = test_dispatcher.RunTests(
         [], MockRunner, ['0', '1'], shard=True)
     self.assertEqual(len(results.GetAll()), 0)
     self.assertEqual(exit_code, constants.ERROR_EXIT_CODE)
 
+  def testTestsRemainWithAllDevicesOffline(self):
+    attached_devices = android_commands.GetAttachedDevices
+    android_commands.GetAttachedDevices = lambda: []
+    try:
+      with self.assertRaises(AssertionError):
+        results, exit_code = TestShard._RunShard(MockRunner)
+    finally:
+      android_commands.GetAttachedDevices = attached_devices
+
 
 class TestReplicate(unittest.TestCase):
   """Tests test_dispatcher.RunTests with replication."""
   @staticmethod
   def _RunReplicate(runner_factory):
     return test_dispatcher.RunTests(
         ['a', 'b', 'c'], runner_factory, ['0', '1'], shard=False)
 
   def testReplicate(self):
     results, exit_code = TestReplicate._RunReplicate(MockRunner)
     # We expect 6 results since each test should have been run on every device
     self.assertEqual(len(results.GetPass()), 6)
     self.assertEqual(exit_code, 0)
 
   def testFailing(self):
     results, exit_code = TestReplicate._RunReplicate(MockRunnerFail)
     self.assertEqual(len(results.GetPass()), 0)
     self.assertEqual(len(results.GetFail()), 6)
     self.assertEqual(exit_code, constants.ERROR_EXIT_CODE)
 
   def testNoTests(self):
     results, exit_code = test_dispatcher.RunTests(
         [], MockRunner, ['0', '1'], shard=False)
     self.assertEqual(len(results.GetAll()), 0)
     self.assertEqual(exit_code, constants.ERROR_EXIT_CODE)
 
 
 if __name__ == '__main__':
   unittest.main()