Arcanist unit tests take several minutes

Question

We have a legacy codebase which we've just started adding unit test coverage. This means that while we have a massive codebase (1.5million lines, at least 600 classes, plus support, template files), we only have one or two unit tests in the entire application. (Sad but true).

My problem is that arcanist unit testing (either with arc unit or part of arc diff) takes over four minutes to run. PHPUnit, on the other hand takes only seconds.

Unit tests are supposed to be short, especially if it's only on the most recent diff. How do I speed these up, or, barring that, see what arcanist is trying to do (so I can optimize myself)?

My best guess is that this has to do with the fact that arcanist needs to look for a test file, while PHPUnit does not, but in that case I don't know how to make arcanist default to the right directory.

This [**answer**](https://stackoverflow.com/a/25930854/319204) describes setting up a `.arcconfig` to point to a `phpunit` test using `PhpunitTestEngine`. Other than that i suspect `arc unit` / `arc diff` spend quite sometime identifying the changes. You could confirm this by checking whether `arc unit --everything` runs faster. — TheCodeArtist, Dec 24 '16 at 17:21

score 0 · Accepted Answer · answered May 11 '17 at 21:38

It turns out that this is actually caused not by the testing but by the coverage. By default Arcanist tries to provide code coverage reports:

   PASS   14ms★  Test\Unicorn\Feeds\Somber\DubStep::testLoadBadType
   PASS    5ms★  Test\Unicorn\Feeds\Somber\DubStep::testLoadBadJSON
   PASS    8ms★  Test\Unicorn\Feeds\Somber\DubStep::testLoadBadSeasonWeek
   PASS  148ms   Test\Unicorn\Feeds\Somber\DubStep::testEmptyData
   PASS  200ms   Test\Unicorn\Feeds\Somber\DubStep::testCompleteLoad
   PASS    5ms★  Test\Fantasy\Feeds\Somber\DubStep::testGetProjectionStats
   PASS    5ms★  Test\Fantasy\Feeds\Somber\DubStep::testGetNumGamesPlayed
   PASS   12ms★  Test\Unicorn\Feeds\Somber\DubStep::testIsStatBonus
   PASS  140ms   Test\Fantasy\Feeds\Somber\DubStep::testIsPlayerUpdatedBaseConditions
   PASS    7ms★  Test\Fantasy\Feeds\Somber\DubStep::testCalcNormalizedWeekProjection

COVERAGE REPORT
      0%     tests/feeds/lib/Feeds/Somber/Extension/usfoak-qub-te-hk3.json
      0%     tests/feeds/lib/Feeds/Somber/DubStep.php
     93%     feeds/lib/Feeds/Somber/PlayerProjectedStats.php

The coverage it runs a complete coverage report against the entire repository, and it doesn't cache the result. This means each file in each arc diff has a coverage report run. In a small project that's not a big deal, but in a large project that makes a major difference. The best way to avoid this is use phpunit coverage report directly and use --no-coverage flag in all of your arc diffs.

Arcanist unit tests take several minutes

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