Mock timer for Telemetry unit tests

Mock timer for Telemetry unit tests

Add a mock timer for Telemetry unit tests to avoid relying on real timers.

BUG=364317
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266009

[Dominik Grewe, 2014-04-17 14:30:51]

I've not changed WaitActionTest.testWaitActionTimeout to use the mock timer,
because it would require plumbing all the way down to
telemetry.core.util.WaitFor. Let me know if you think that's needed though.
PTAL.

[Sami, 2014-04-17 15:43:22]

What to do with testWaitActionTimeout really depends on what we want it to test:
if it's supposed to be a unit test for WaitAction, then we could just mock out
tab.WaitForJavaScriptExpression; if it's trying to verify that timing out JS
evaluation in the browser works. However in the latter case we should move it
to, say, tab_unittest.py.

Third option: why not both? :)

[tonyg, 2014-04-17 16:18:25]

I'm pretty much okay with whatever we decide here, but I just want to point out
the MockTimer pattern here:
https://code.google.com/p/chromium/codesearch#chromium/src/tools/perf/metrics...

My vote would be something that tests as end-to-end as possible, except with a
deterministic timer injected.

[Dominik Grewe, 2014-04-17 16:44:53]

On 2014/04/17 16:18:25, tonyg wrote:
> I'm pretty much okay with whatever we decide here, but I just want to point
out
> the MockTimer pattern here:
>
https://code.google.com/p/chromium/codesearch#chromium/src/tools/perf/metrics...

That MockTimer advances the time randomly (in a given range). I don't think we'd
have any advantages doing that here. Or are you just referring to the API?

> 
> My vote would be something that tests as end-to-end as possible, except with a
> deterministic timer injected.

As I said, that would require plumbing the timer all the way through to the
util.WaitFor function. If that's acceptable I'm happy to do it.

[Dominik Grewe, 2014-04-22 17:45:52]

I've added the mock timer to the timeout test. Is this what you had in mind,
Tony?

[tonyg, 2014-04-22 18:17:06]

Sorry for the delay, I've been OOO.

I like this approach but don't think the plumbing is necessary in python. Check
out how perf_profiler_unittest uses simple_mock to mock out subprocess for
example.

[Dominik Grewe, 2014-04-23 09:56:25]

On 2014/04/22 18:17:06, tonyg wrote:
> Sorry for the delay, I've been OOO.
> 
> I like this approach but don't think the plumbing is necessary in python.
Check
> out how perf_profiler_unittest uses simple_mock to mock out subprocess for
> example.

Okay. I considered using the simple_mock.MockObject to hide wait.time and
util.time. But MockObject seems to assume that we know the exact order of
function calls to that object. That would require us to hard-code the time-out
mechanism into the test.

Instead, I'm now hiding time.sleep and time.time explicitly with the MockTimer
methods. PTAL.

[tonyg, 2014-04-24 03:55:25]

lgtm

[commit-bot: I haz the power, 2014-04-24 03:55:57]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dominikg@chromium.org/240893004/80001

[commit-bot: I haz the power, 2014-04-24 05:18:37]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-04-24 05:18:37]

Try jobs failed on following builders:
  tryserver.chromium on linux_chromium_chromeos_rel
  tryserver.chromium on win_chromium_x64_rel

[Dominik Grewe, 2014-04-24 09:25:26]

The CQ bit was checked by dominikg@chromium.org

[commit-bot: I haz the power, 2014-04-24 09:25:40]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dominikg@chromium.org/240893004/80001

[commit-bot: I haz the power, 2014-04-24 11:29:48]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-04-24 11:29:49]

Try jobs failed on following builders:
  tryserver.chromium on linux_chromium_chromeos_rel

[Dominik Grewe, 2014-04-24 11:53:04]

The CQ bit was checked by dominikg@chromium.org

[commit-bot: I haz the power, 2014-04-24 11:53:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dominikg@chromium.org/240893004/80001

[commit-bot: I haz the power, 2014-04-24 14:18:31]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-04-24 14:18:31]

Try jobs failed on following builders:
  tryserver.chromium on linux_chromium_chromeos_rel

[tonyg, 2014-04-24 14:22:18]

The CQ bit was checked by tonyg@chromium.org

[commit-bot: I haz the power, 2014-04-24 14:23:01]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dominikg@chromium.org/240893004/80001

[commit-bot: I haz the power, 2014-04-24 22:24:29]

Change committed as 266009