Jest

To use Captain with Jest, 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

Jest can output test results to a file using the --json, --testLocationInResults, and --outputFile flags. Configure Captain by creating a .captain/config.yml file in the root directory of your repository:

test-suites:
  your-project-jest:
    command: npx jest --json --testLocationInResults --outputFile tmp/jest.json
    results:
      path: tmp/jest.json

You can change your-project-jest to any name you like, but we typically recommend using the name of your project followed by a dash followed by jest. 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 npx jest and want to store test results in tmp/jest.json.

Once Captain is configured, you can run captain run your-project-jest --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 Jest, 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-jest \
  --file jest/sum.test.js  \
  --description "adds 1 + 2 to equal 3"

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-jest:
    command: npx jest --json --testLocationInResults --outputFile tmp/jest.json
    results:
      path: tmp/jest.json
    output:
      print-summary: true
    retries:
      attempts: 2
      command: npx jest --testPathPattern '{{ testPathPattern }}' --testNamePattern '{{ testNamePattern }}' --json --testLocationInResults --outputFile tmp/jest.json

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-jest:
    command: npx jest --json --testLocationInResults --outputFile tmp/jest.json
    results:
      path: tmp/jest.json
    output:
      print-summary: true
    partition:
      command: npx jest --testPathPattern {{ testFiles }} --json --testLocationInResults --outputFile tmp/jest.json
      delimiter: '|'
      globs:
        - '**/*.test.js'

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

Also note that Jest uses a custom partition.delimiter of |.

Then partition across your CI provider's parallel jobs:

# .rwx/ci.yml

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

  - key: node
    call: nodejs/install 1.1.14
    with:
      node-version: 20

  - key: deps
    use: [code, node]
    run: npm ci

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

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

Usage with ABQ

Captain works with ABQ to support parallel test distribution while respecting the quarantine status of any tests. To use Captain with ABQ, the Captain CLI will wrap ABQ and ABQ will wrap your test suite. For example:

test-suites:
  your-project-jest:
    command: bash -c "abq test --worker $ABQ_WORKER --reporter rwx-v1-json=tmp/abq.json -- npx jest"
    results:
      path: tmp/abq.json

ABQ_WORKER=0 captain run your-project-jest