ExUnit

To use Captain with ExUnit, you need to configure your test suite to output test results to a file and then tell Captain where to find those test results.

Getting Started

ExUnit does not natively produce a test results artifact that Captain can parse. To integrate, you'll need to install and configure the junit_formatter package. Once installed, you can configure it by making these changes to your test/test_helper.exs and config/test.exs:

# test/test_helper.exs

ExUnit.configure formatters: [JUnitFormatter, ExUnit.CLIFormatter]

# config/test.exs

config :junit_formatter,
  report_dir: Path.expand("../tmp/junit", __DIR__),
  project_dir: Path.expand("..", __DIR__),
  automatic_create_dir?: true,
  print_report_file: true,
  prepend_project_name?: true,
  include_filename?: true,
  include_file_line?: true

Once you have junit_formatter installed and configured, configure Captain by creating a .captain/config.yml file in the root directory of your repository:

test-suites:
  your-project-exunit:
    command: mix test
    results:
      language: Elixir
      framework: ExUnit
      path: tmp/junit/*.xml

You can change your-project-exunit to any name you like, but we typically recommend using the name of your project followed by a dash followed by exunit. The command is the command you already use to run your test suite. Captain will invoke this command to run your tests. The example above shows what you might use if you use mix test and want to store test results in tmp/junit.

Once Captain is configured, you can run captain run your-project-exunit --print-summary. If you see your typical test output followed by a captain block like this:

--------------------------------------------------------------------------------
----------------------------------- Captain ------------------------------------
--------------------------------------------------------------------------------

then you've configured everything correctly! You can now supercharge your test framework's capabilities. See below for configuring each of Captain's features.

Identifying Tests

Captain uses framework specific "identity recipes" to identify the tests in your suite. These recipes are order dependent components extracted from native test framework output.

We use this identity to track the executions of a test over the course of their lifetime in your suite. This enables us to do things like flake detection, quarantining, and retries.

For ExUnit, Captain constructs the identity by parsing out the file and description attributes.

Quarantining Tests

Captain makes managing flaky tests easier than ever. When a test is identified as flaky, you can quarantine the test without modifying it, so that if only those tests fail, Captain reports a success with a 0 exit code. Unlike skipped tests, quarantined tests will continue to run, so you can still view their failure messages and see how frequently they are failing.

You can quarantine tests in OSS mode with captain add quarantine like so:

captain add quarantine your-project-exunit \
  --file test/exunitexample_web/controllers/page_controller_test.exs  \
  --description "Elixir.ExunitexampleWeb.PageControllerTest test GET /"

See the OSS quarantining guide for more information on managing quarantined tests in OSS mode.

Retrying Tests

You can configure Captain to automatically retry failed tests to help you determine if failing tests are flaky or are genuinely failing. To configure retries, update your .captain/config.yml file like so:

test-suites:
  your-project-exunit:
    command: mix test
    results:
      language: Elixir
      framework: ExUnit
      path: tmp/junit/*.xml
    output:
      print-summary: true
    retries:
      attempts: 2
      command: mix test {{ tests }}

Once configured, Captain will invoke your original test command, check for any failures, and retry your tests however many times you've specified (in this example, two additional times) by templating the failures into the command specified by retries.command. The output.print-summary option is not required, but we've added it for convenience in understanding the overall results after the retries have been factored in.

Partitioning

Captain can optimally partition your test suite's files into multiple groups for execution on multiple CI nodes. Captain tracks your test file runtime so that it can balance each partition.

Configure partitioning in .captain/config.yml:

test-suites:
  your-project-exunit:
    command: mix test
    results:
      language: Elixir
      framework: ExUnit
      path: tmp/junit/*.xml
    output:
      print-summary: true
    partition:
      command: mix test {{ testFiles }}
      globs:
        - tests/**/*_test.exs

Captain will fill in the testFiles placeholder of your partition.command with the files resulting from expanding your configured partition.globs.

Then partition across your CI provider's parallel jobs:

# .rwx/ci.yml

tasks:
  - key: code
    call: git/clone 2.0.7

  - key: erlang
    call: erlang/install 1.1.3
    with:
      erlang-version: '26'

  - key: elixir
    call: elixir-lang/install 1.1.4
    use: erlang
    with:
      elixir-version: '1.16'

  - key: deps
    use: [code, elixir]
    run: mix deps.get

  - key: captain
    call: rwx/install-captain 1.1.6

  - key: exunit
    use: [deps, captain]
    parallel: 8
    run: captain run your-project-exunit