[android] Add timeout_retry module to pylib/utils/.

build/android/pylib/utils/timeout_retry_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 timeout_and_retry.py."""
+
+import time
+import unittest
+
+import reraiser_thread
+import timeout_retry
+
+
+class TestException(Exception):
+  pass
+
+
+def _NeverEnding(tries=[0]):
+  tries[0] += 1
+  while True:
+    pass
+
+
+def _CountTries(tries):
+  tries[0] += 1
+  raise TestException
+
+
+class TestRun(unittest.TestCase):
+  """Tests for timeout_retry.Run."""
+
+  def testRun(self):
+    self.assertTrue(timeout_retry.Run(
+        lambda x: x, 30, 3, [True], {}))
+
+  def testTimeout(self):
+    tries = [0]
+    start = time.time()
+    self.assertRaises(reraiser_thread.TimeoutError,
+        timeout_retry.Run, lambda: _NeverEnding(tries), 0, 3)
+    self.assertLess(time.time() - start, 2)

[frankf, 2013/11/14 23:26:05]

this seems flaky. Is this guranteed to be true under all conditions, however
unlikely?

[craigdh, 2013/11/15 00:26:30]

It is probably theoretically possible it could fail... but it's not
realistically going to happen. There is no sleep() occurring with a 0 timeout so
it won't fail as long as the code between those locations takes less than two
seconds to execute which seems a fair assumption. I don't think there's a better
way to verify the timeout time is working.

[frankf, 2013/11/15 23:08:47]

If this is an infinite loop, then it should be sufficient to assert a
TimeoutError is raised. I don't see any value in asserting the exact wallclock
time it took.

On 2013/11/15 00:26:30, craigdh wrote:

[craigdh, 2013/11/15 23:41:57]

Ok, that's reasonable.

+    self.assertEqual(tries[0], 3)
+
+  def testRetries(self):
+    tries = [0]
+    self.assertRaises(TestException,
+        timeout_retry.Run, lambda: _CountTries(tries), 30, 3)
+    self.assertEqual(tries[0], 3)
+
+  def testReturnValue(self):
+    self.assertTrue(timeout_retry.Run(lambda: True, 30, 3))
+
+
+if __name__ == '__main__':
+  unittest.main()