Split Test Parallelization

ember exam --split=<num> --parallel

The parallel option allows you to run your split tests across multiple test pages in parallel in Testem. It will use a separate browser instance for each group of tests. So, if you specify a split of 3, then 3 browser instances will be spawned with the output looking something like:

ok 1 PhantomJS 1.9 - Exam Partition 1 - some test
ok 2 PhantomJS 1.9 - Exam Partition 3 - some other other test
ok 3 PhantomJS 1.9 - Exam Partition 2 - some other test

You can also combine the parallel option with the partition option to split tests, and then recombine partitions into parallel runs. This would, for example, allow you to run tests in multiple CI containers and have each CI container parallelize its list of tests.

For example, if you wanted to run your tests across two containers, but have one of them run twice as many tests as the other, and run them in parallel, you could do this:

# container 1
ember exam --split=3 --partition=1,2 --parallel

# container 2
ember exam --split=3 --partition=3 --parallel

Note 1: Ember Exam will respect the parallel setting of your Testem config file while running tests in parallel. The default value for parallel in Testem is 1, which means you'll need a non-default value to actually see parallel behavior.

Note 2: Ember Exam sets process.env.EMBER_EXAM_SPLIT_COUNT for convenience. You can use this in your Testem file.

Note 3: You must be using Testem version 1.5.0 or greater for this feature to work properly.