Buildkite Test Splitter

Buildkite Test Splitter is an open source tool to orchestrate your test suites. It uses your Buildkite Test Analytics suite data to intelligently partition and parallelise your tests. Test Splitter currently only supports RSpec but support for other frameworks is coming soon.

Migrating to 0.9.0

Version 0.9.0 introduces a new feature that requires Test Splitter to read test results from the runner for retries and verification purposes. To enable this feature, it is necessary to configure the BUILDKITE_SPLITTER_RESULT_PATH environment variable. This variable specifies the location of where the runner should store test results.

Furthermore, we have updated the default test command for RSpec to bundle exec rspec --format progress --format json --out {{resultPath}} {{testExamples}}. Test Splitter will automatically replace {{resultPath}} with the value specified in BUILDKITE_SPLITTER_RESULT_PATH. If you want to customize the RSpec command, make sure to include --format json --out {{resultPath}} in the command.

Installation

The latest version of Buildkite Test Splitter can be downloaded from https://github.com/buildkite/test-splitter/releases

Supported OS/Architecture

ARM and AMD architecture for linux and darwin

The available Go binaries

• test-splitter-darwin-amd64
• test-splitter-darwin-arm64
• test-splitter-linux-amd64
• test-splitter-linux-arm64

Using the Test Splitter

ENV variables

Test Splitter uses the following Buildkite provided environment variables. Please make sure that the following environment variables are available in your testing environment, particularly if you use Docker or some other type of containerization to run your tests.

Environment Variable	Description
BUILDKITE_BUILD_ID	The UUID of the Buildkite build. Test Splitter uses this UUID along with BUILDKITE_STEP_ID to uniquely identify the test plan.
BUILDKITE_JOB_ID	The UUID of the job in Buildkite build.
BUILDKITE_ORGANIZATION_SLUG	The slug of your Buildkite organization.
BUILDKITE_PARALLEL_JOB	The index number of a parallel job created from a Buildkite parallel build step. Make sure you configure parallelism in your pipeline definition. You can read more about Buildkite parallel build step on this page.
BUILDKITE_PARALLEL_JOB_COUNT	The total number of parallel jobs created from a Buildkite parallel build step. Make sure you configure parallelism in your pipeline definition. You can read more about Buildkite parallel build step on this page.
BUILDKITE_STEP_ID	The UUID of the step group in Buildkite build. Test Splitter uses this UUID along with BUILDKITE_BUILD_ID to uniquely identify the test plan.

In addition to the above variables, you must set the following environment variables.

Environment Variable	Description
BUILDKITE_SPLITTER_API_ACCESS_TOKEN	Buildkite API access token with read_suites, read_test_plan, and write_test_plan scopes. You can create an access token from Personal Settings in Buildkite
BUILDKITE_SPLITTER_SUITE_SLUG	The slug of your Buildkite Test Analytics test suite. You can find the suite slug in the url for your suite. For example, the slug for the url: https://buildkite.com/organizations/my-organization/analytics/suites/my-suite is my-suite
BUILDKITE_SPLITTER_RESULT_PATH	Test Splitter uses this environment variable to tell the runner where to store the test result. Test Splitter reads the test result after each test run for retries and verification. For RSpec, the result is generated using the --format json and --out CLI options, while for Jest, it is generated using the --json and --outputFile options. We have included these options in the default test command for RSpec and Jest. If you need to customize your test command, make sure to append the CLI options to save the result to a file. Please refer to the BUILDKITE_SPLITTER_TEST_CMD environment variable for more details. *Note: Test Splitter will not delete the file after running the test, however it will be deleted by Buildkite Agent as part of build lifecycle. *

The following environment variables can be used optionally to configure your Test Splitter.

Environment Variable	Default Value	Description
BUILDKITE_SPLITTER_DEBUG_ENABLED	false	Flag to enable more verbose logging.
BUILDKITE_SPLITTER_RETRY_CMD	BUILDKITE_SPLITTER_TEST_CMD	The command to retry the failed tests. Test Splitter will fill in the {{testExamples}} placeholder with the failed tests. If not set, the Test Splitter will use the same command defined in BUILDKITE_SPLITTER_TEST_CMD.
BUILDKITE_SPLITTER_RETRY_COUNT	0	The number of retries. Test Splitter runs the test command defined in BUILDKITE_SPLITTER_TEST_CMD and retries only the failed tests up to BUILDKITE_SPLITTER_RETRY_COUNT times, using the retry command defined in BUILDKITE_SPLITTER_RETRY_CMD.
BUILDKITE_SPLITTER_SPLIT_BY_EXAMPLE	false	Flag to enable split by example. When this option is true, the Test Splitter will split the execution of slow test files over multiple partitions.
BUILDKITE_SPLITTER_TEST_CMD	bundle exec rspec --format progress --format json --out {{resultPath}} {{testExamples}}	Test command to run your tests. Test Splitter will replace the {{testExamples}} placeholder with the test splitting results, and replace {{resultPath}} with the value set in BUILDKITE_SPLITTER_RESULT_PATH. It is necessary to configure your Rspec with --format json --out {{resultPath}} when customizing the test command, because Test Splitter needs to read the result after each test run.
BUILDKITE_SPLITTER_TEST_FILE_EXCLUDE_PATTERN	-	Glob pattern to exclude certain test files or directories. The exclusion will be applied after discovering the test files using a pattern configured with BUILDKITE_SPLITTER_TEST_FILE_PATTERN. This option accepts the pattern syntax supported by the zzglob library.
BUILDKITE_SPLITTER_TEST_FILE_PATTERN	spec/**/*_spec.rb	Glob pattern to discover test files. You can exclude certain test files or directories from the discovered test files using a pattern that can be configured with BUILDKITE_SPLITTER_TEST_FILE_EXCLUDE_PATTERN. This option accepts the pattern syntax supported by the zzglob library.
BUILDKITE_SPLITTER_TEST_RUNNER	rspec	Test runner to use for running tests. Currently only rspec is supported.

Run the Test Splitter

Please download the executable and make it available in your testing environment. To parallelize your tests in your Buildkite build, you can amend your pipeline step configuration to:

steps:
  - name: "Rspec"
    command: ./test-splitter
    parallelism: 10
    env:
      BUILDKITE_SPLITTER_SUITE_SLUG: my-suite
      BUILDKITE_SPLITTER_API_ACCESS_TOKEN: your-secret-token

Possible exit statuses

The test-splitter client may exit with a variety of exit statuses, outlined below:

• If there is a configuration error, the test-splitter client will exit with status 16.
• If the test-splitter runner (such as RSpec) exits cleanly, the exit status of the runner is returned. This will likely be 0 for successful test runs, 1 for failing test runs, but may be any other error status returned by the runner.
• If the test-splitter runner is terminated by an OS level signal, such as SIGSEGV or SIGABRT, the exit status returned will be equal to 128 plus the signal number. For example, if the runner raises a SIGSEGV, the exit status will be (128 + 11) = 139.