My team has been using Protractor for our end to end tests for a couple months now, and the amount of time the test suite takes to finish has grown as we add more tests. So we started looking for ways to speed our tests up. We already have a Selenium grid running with a few browser instances connected to it. Ideally we would like to split the tests out to be ran in parallel among the browser instances in the grid.

The first configuration setting we tried was setting the count within the capabilities section of the configuration file.

exports.config = {
  capabilities: {
    browserName: 'chrome',
    count: 2
  },

  /* ... more protractor config values ... */
}

We ran Protractor and noticed both browser instances ran the tests. But after closer examination, we realized each browser instance was running all the tests. So the tests were being ran in parallel, but it wasn’t saving us any time because each test was ran twice.

I then dug into the source code for protractor in Github and found an example configuration file with comments about each setting. The comment for the count setting confirmed what we were seeing: ‘Number of times to run this set of capabilities (in parallel, unless limited by maxSessions)’. I continued reading the example configuration file and found what I was looking for right below the count setting.

The comment for shardTestFiles reads: ‘If this is set to be true, specs will be sharded by file (i.e. all files to be run by this set of capabilities will run in parallel). Default is false.’

So then I updated my config to the following and ran Protractor again.

exports.config = {
  capabilities: {
    browserName: 'chrome',
    shardTestFiles: true
  },

  /* ... more protractor config values ... */
}

However, this time only one browser instance ran the tests. They were not sharded between the 2 browser instances connected to the Selenium grid.

I went back to the example config file and then found the maxInstances setting, and read its comment that said this is only needed if shardTestFiles is true. So I added maxInstances to the config and ran Protractor again.

exports.config = {
  capabilities: {
    browserName: 'chrome',
    shardTestFiles: true,
    maxInstances: 2
  },

  /* ... more protractor config values ... */
}

And this time the test files were successfully sharded between the 2 browser instances.

Our tests were taking around 3 minutes to complete when they weren’t split up, and then they took around 2 minutes to complete after we split them among 2 browsers. So we weren’t able to realize a 50% reduction in the overall test time by splitting the tests between two browsers, but our overall test time was significantly improved.

PS

The shardTestFiles configuration was introduced in version 0.24. So if you’re running an earlier version then your test files will not be sharded.