filtering mochitests for remote testing

One major problem we encounter in running all our unittests on Fennec is the large volume of failures and how to manage them.  Currently we have turned off mochitests on the Maemo tinderbox because nobody looked at the results (we still run reftest/crashtest/xpcshell!)

In many of my previous posts, I outlined methods for running tests remotely and that has proven to be very useful.  In order to test this code and continue developing it (without windows mobile or a working android build yet), I have developed a simple python test-agent that can run on a linux box (including n900.)  If you are curious, check it out and watch tests run remotely…it is pretty cool.

So the real problem I need to solve is how to not run a list of tests on a mobile device.  Solving this could get us to green faster and reduce the mochitest runtime in half!

In 2008 my solution was Maemkit.  Maemkit is just a small wrapper around the python test runner scripts that does some file (renaming) and directory (splitting into smaller chunks) manipulation to allow for more reliable test runs.  This has worked great and still works.  Enter remote testing and we need to hack up Maemkit a lot to accommodate for everything.  In addition a lot of the work maemkit does is already in the test runners.

Today I have moved the filtering to be a bit more configurable and less obscure.  This is really just a prototype and toolset to solve a problem for me locally, but the idea is something worth sharing.  What I have done is built up a json file (most of this was done automatically with this parsing script) which outlines the test and has some ‘tags’ that I can filter on:

   {
     "fennec-tags" : {"orange": "", "remote": "", "timeout": ""},
     "name" : "/tests/toolkit/content/tests/widgets/test_tooltip.xul"
   },
   {
     "fennec-results" : {"fail": 0, "todo": 0, "pass": 51},
     "name" : "/tests/MochiKit_Unit_Tests/test_MochiKit-Async.html",
     "note" : []
   }

You can see I now can run or skip tests that are tagged ‘orange’ or ‘timeout’. Better yet, I can skip tests with fennec-results that match fail > 0 if I want everything to be green.

So I took this a bit further since I wanted to turn these on or off depending on if I wanted to run tests or to investigate bugs, and I allowed for a filter language to be parsed in mochitest/tests/SimpleTest/setup.js.  I then modified my runtestsremote.py (subclass of runtests.py) so when launching mochitest from the command line I could control this like:

#run all tests that match the 'orange' tag
python runtestsremote.py --filter='run:fennec-tags(orange)'

#skip all tests that have the timeout tag
python runtestsremote.py --filter='skip:fennec-tags(timeout)'

#skip all tests that have failures > 0
python runtestsremote.py --filter='skip:fennec-results(fail>0)'

You should now see the power of this filtering and that with some more detailed thinking we could have a powerful engine to run what we want.  Of course this can run on regular mochitest (if you take the code in this patch from runtestsremote.py and add it to runtests.py.in) and run all the orange tests in a loop or something like that.

As a note, I previously mentioned a parsing script.   With some cleanup you could automatically create this json filter file based on tinderbox runs and fill in the tags to identify scenarios like orange (failing sometimes), timeouts, focus problems, etc…

Happy filtering!