[!WARNING] Knapsack is archived. But Knapsack Pro is available.

Knapsack Pro comes with a free plan and discounts on paid plans for people coming from Knapsack (see how to migrate in 10 minutes).

This repository remains available to fork and the gem hosted on RubyGems, so your existing setup won't be affected.

Knapsack wraps your current test runner and works with your existing CI infrastructure to split tests optimally.

It comes in two flavors, knapsack and knapsack_pro:

Migrate from knapsack to knapsack_pro

If you already use knapsack and want to give knapsack_pro a try, here's how to migrate in 10 minutes.

knapsack

Knapsack generates a test time execution report and uses it for future test runs.

The knapsack gem supports:

• RSpec
• Cucumber
• Minitest
• Spinach
• Turnip

Without Knapsack - bad test suite split

With Knapsack - better test suite split

Requirements

>= Ruby 2.1.0

• Update
• Installation
• Usage
  • Step for RSpec
  • Step for Cucumber
  • Step for Minitest
  • Step for Spinach
  • Custom configuration
  • Common step
    • Adding or removing tests
• Set up your CI server
  • Info about ENV variables
  • Passing arguments to the Rake task
    • Passing arguments to RSpec
    • Passing arguments to Cucumber
    • Passing arguments to Minitest
    • Passing arguments to Spinach
  • Knapsack binary
  • CircleCI
    • Step 1
    • Step 2
  • Travis
    • Step 1
    • Step 2
  • Semaphore
    • Step 1
    • Step 2
      • Semaphore 2.0
  • Buildkite
    • Step 1
    • Step 2
  • GitLab CI
    • Step 1
    • Step 2
  • Info for Jenkins
  • Info for BitBucket Pipelines
    • Step 1
    • Step 2
• FAQ
  • What does time offset warning mean?
  • How to generate the Knapsack report?
  • What does "leftover specs" mean?
  • Why are there "leftover specs" after I generate a new report?
  • How can I run tests from multiple directories?
  • How to update the existing Knapsack report for a few test files?
  • How to run tests for particular CI node in your development environment
  • How can I change the log level?
• Gem tests
  • Spec
  • Spec examples
• Acknowledgements
• Mentions

Update

Please check CHANGELOG.md before updating the gem. Knapsack follows semantic versioning.

Installation

Add these lines to your application's Gemfile:

group :test, :development do
  gem 'knapsack'
end

And then execute:

bundle

Add this line at the bottom of Rakefile:

Knapsack.load_tasks if defined?(Knapsack)

Usage

Here's an example of a Rails app with Knapsack.

https://github.com/KnapsackPro/rails-app-with-knapsack

Step for RSpec

Add at the beginning of your spec_helper.rb:

require 'knapsack'

# CUSTOM_CONFIG_GOES_HERE

Knapsack::Adapters::RSpecAdapter.bind

Step for Cucumber

Create features/support/knapsack.rb:

require 'knapsack'

# CUSTOM_CONFIG_GOES_HERE

Knapsack::Adapters::CucumberAdapter.bind

Step for Minitest

Add the Knapsack code after you load the app environment in test/test_helper.rb:

ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
require 'rails/test_help'

require 'knapsack'

# CUSTOM_CONFIG_GOES_HERE

knapsack_adapter = Knapsack::Adapters::MinitestAdapter.bind
knapsack_adapter.set_test_helper_path(__FILE__)

Step for Spinach

Create features/support/env.rb:

require 'knapsack'

# CUSTOM_CONFIG_GOES_HERE

Knapsack::Adapters::SpinachAdapter.bind

Custom configuration

You can change the default Knapsack configuration for RSpec, Cucumber, Minitest, or Spinach tests.

Here are some examples (that you can insert in CUSTOM_CONFIG_GOES_HERE):

Knapsack.tracker.config({
  enable_time_offset_warning: true,
  time_offset_in_seconds: 30
})

Knapsack.report.config({
  test_file_pattern: 'spec/**{,/*/**}/*_spec.rb', # default value based on adapter
  report_path: 'knapsack_custom_report.json'
})

# You can use your logger:
require 'logger'
Knapsack.logger = Logger.new(STDOUT)
Knapsack.logger.level = Logger::INFO

Common step

Generate the time execution report for your test files. Run the command below on one of your CI nodes:

# Step for RSpec:
KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

# Step for Cucumber:
KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features

# Step for Minitest:
KNAPSACK_GENERATE_REPORT=true bundle exec rake test

# If you use Rails 5.0.x then run this instead:
KNAPSACK_GENERATE_REPORT=true bundle exec rake test

# If you use Rails >= 5.1's SystemTest, run both unit and system tests:
KNAPSACK_GENERATE_REPORT=true bundle exec rake test test:system

# Step for Spinach:
KNAPSACK_GENERATE_REPORT=true bundle exec spinach

Commit the generated report knapsack_rspec_report.json, knapsack_cucumber_report.json, knapsack_minitest_report.json or knapsack_spinach_report.json into your repository.

This report should be updated after you add a lot of new slow tests or you change existing ones, which causes a big time execution difference between CI nodes.

You will get a time offset warning at the end of the RSpec/Cucumber/Minitest run, which reminds you when it’s a good time to regenerate the Knapsack report.

KNAPSACK_GENERATE_REPORT is truthy with "true" or 0. All other values are falsy, though "false" and 1 are semantically preferrable.

Adding or removing tests

There is no need to regenerate the report every time you add/remove test files.

If you remove a test file, Knapsack will ignore its entry in the report. If you add a new test file that is not listed in the report, the test file will be assigned to one of the CI nodes.

You'll want to regenerate your execution report whenever you remove or add a test file with a long time execution time that would affect one of the CI nodes. Knapsack warns you when it's a good time to regenerate the report.

Set up your CI server

On your CI server, run the following command for the first CI node (increase CI_NODE_INDEX for the next nodes):

# Step for RSpec:
CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:rspec

# Step for Cucumber:
CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:cucumber

# Step for Minitest:
CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:minitest

# Step for Spinach:
CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:spinach

You can add KNAPSACK_TEST_FILE_PATTERN if your tests are not in the default directory:

# Step for RSpec:
KNAPSACK_TEST_FILE_PATTERN="directory_with_specs/**{,/*/**}/*_spec.rb" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:rspec

# Step for Cucumber:
KNAPSACK_TEST_FILE_PATTERN="directory_with_features/**/*.feature" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:cucumber

# Step for Minitest:
KNAPSACK_TEST_FILE_PATTERN="directory_with_tests/**{,/*/**}/*_spec.rb" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:minitest

# Step for Spinach:
KNAPSACK_TEST_FILE_PATTERN="directory_with_features/**/*.feature" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:spinach

You can set KNAPSACK_REPORT_PATH if your Knapsack report was saved in a non-default location:

# Step for RSpec:
KNAPSACK_REPORT_PATH="knapsack_custom_report.json" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:rspec

# Step for Cucumber:
KNAPSACK_REPORT_PATH="knapsack_custom_report.json" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:cucumber

# Step for Minitest:
KNAPSACK_REPORT_PATH="knapsack_custom_report.json" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:minitest

# Step for Spinach:
KNAPSACK_REPORT_PATH="knapsack_custom_report.json" CI_NODE_TOTAL=2 CI_NODE_INDEX=0 bundle exec rake knapsack:spinach

Info about ENV variables

CI_NODE_TOTAL - total number of CI nodes you have.

CI_NODE_INDEX - index of the current CI node starting from 0 (ie, the second CI node should have CI_NODE_INDEX=1).

Some CI providers like GitLab CI have the same name of environment variable like CI_NODE_INDEX, which starts from 1 instead of 0. Knapsack will automatically pick it up and change it from 1 to 0.

Passing arguments to the Rake task

Passing arguments to RSpec

Knapsack allows you to pass arguments through to RSpec. For example, if you want to run only specs that have the tag focus. If you do this with RSpec directly, it would look like:

bundle exec rake rspec --tag focus

To do this with Knapsack, you simply add your RSpec arguments as parameters to the Knapsack Rake task:

bundle exec rake "knapsack:rspec[--tag focus]"

Remember that using tags to limit which specs get run will affect the time each file takes to run. One solution to this is to generate a new knapsack_rspec_report.json for the commonly run scenarios.

Passing arguments to Cucumber

bundle exec rake "knapsack:cucumber[--name feature]"

Passing arguments to Minitest

bundle exec rake "knapsack:minitest[--arg_name value]"

For instance, to run verbose tests:

bundle exec rake "knapsack:minitest[--verbose]"

Passing arguments to Spinach

bundle exec rake "knapsack:spinach[--name feature]"

Knapsack binary

You can install knapsack globally and use the binary:

knapsack rspec "--tag custom_tag_name --profile"
knapsack cucumber
knapsack minitest "--verbose --pride"
knapsack spinach "-f spinach_examples"

Here's an example when it might be useful.

CircleCI

If you are using circleci.com, you can omit CI_NODE_TOTAL and CI_NODE_INDEX. Knapsack will use the CIRCLE_NODE_TOTAL and CIRCLE_NODE_INDEX provided by CircleCI.

Here is an example for test configuration in your .circleci/config.yml file:

Step 1

Run all the tests on a single CI node with the enabled report generator:

# CircleCI 2.0
- run:
  name: Step for RSpec
  command: |
    # export is important here
    export KNAPSACK_GENERATE_REPORT=true
    bundle exec rspec spec

- run:
  name: Step for Cucumber
  command: |
    # export is important here
    export KNAPSACK_GENERATE_REPORT=true
    bundle exec cucumber features

- run:
  name: Step for Minitest
  command: |
    # export is important here
    export KNAPSACK_GENERATE_REPORT=true
    bundle exec rake test
    # For Rails 5.1 runs unit and system tests
    bundle exec rake test test:system

- run:
  name: Step for Spinach
  command: |
    # export is important here
    export KNAPSACK_GENERATE_REPORT=true
    bundle exec rspec spinach

After the tests pass, you should copy the Knapsack JSON report and commit it into your repository as knapsack_rspec_report.json, knapsack_cucumber_report.json, knapsack_minitest_report.json or knapsack_spinach_report.json.

Step 2

Update the test command and enable parallelism (remember to add additional containers for your project in the CircleCI settings):

# CircleCI 2.0
- run:
  name: Step for RSpec
  command: bundle exec rake knapsack:rspec

- run:
  name: Step for Cucumber
  command: bundle exec rake knapsack:cucumber

- run:
  name: Step for Minitest
  command: bundle exec rake knapsack:minitest

- run:
  name: Step for Spinach
  command: bundle exec rake knapsack:spinach

Travis

Step 1

Run all the tests on a single CI node with the enabled report generator. Edit .travis.yml:

script:
  # Step for RSpec:
  - "KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec"

  # Step for Cucumber:
  - "KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features"

  # Step for Minitest:
  - "KNAPSACK_GENERATE_REPORT=true bundle exec rake test"
  - "KNAPSACK_GENERATE_REPORT=true bundle exec rake test test:system" # For Rails 5.1 runs unit and system tests

  # Step for Spinach:
  - "KNAPSACK_GENERATE_REPORT=true bundle exec spinach"

After the tests pass, you should copy the Knapsack JSON report and commit it into your repository as knapsack_rspec_report.json, knapsack_cucumber_report.json, knapsack_minitest_report.json or knapsack_spinach_report.json.

Step 2

You can parallelize your builds across virtual machines with the Travis matrix feature. Edit .travis.yml:

script:
  # Step for RSpec:
  - "bundle exec rake knapsack:rspec"

  # Step for Cucumber:
  - "bundle exec rake knapsack:cucumber"

  # Step for Minitest:
  - "bundle exec rake knapsack:minitest"

  # Step for Spinach:
  - "bundle exec rake knapsack:spinach"

env:
  - CI_NODE_TOTAL=2 CI_NODE_INDEX=0
  - CI_NODE_TOTAL=2 CI_NODE_INDEX=1

If you want to have both global and matrix ENVs:

script:
  # Step for RSpec:
  - "bundle exec rake knapsack:rspec"

  # Step for Cucumber:
  - "bundle exec rake knapsack:cucumber"

  # Step for Minitest:
  - "bundle exec rake knapsack:minitest"

  # Step for Spinach:
  - "bundle exec rake knapsack:spinach"

env:
  global:
    - RAILS_ENV=test
    - MY_GLOBAL_VAR=123
    - CI_NODE_TOTAL=2
  jobs:
    - CI_NODE_INDEX=0
    - CI_NODE_INDEX=1

Such configuration will generate a matrix with the two following rows:

CI_NODE_TOTAL=2 CI_NODE_INDEX=0 RAILS_ENV=test MY_GLOBAL_VAR=123
CI_NODE_TOTAL=2 CI_NODE_INDEX=1 RAILS_ENV=test MY_GLOBAL_VAR=123

More info about global and matrix ENV configuration in the Travis docs.

Semaphore

Step 1

Run all the tests on a single CI node with the enabled report generator:

# Step for RSpec
KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

# Step for Cucumber
KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features

# Step for Minitest
KNAPSACK_GENERATE_REPORT=true bundle exec rake test
KNAPSACK_GENERATE_REPORT=true bundle exec rake test test:system # For Rails 5.1 runs unit and system tests

# Step for Spinach
KNAPSACK_GENERATE_REPORT=true bundle exec spinach

After the tests pass, you should copy the Knapsack JSON report and commit it into your repository as knapsack_rspec_report.json, knapsack_cucumber_report.json, knapsack_minitest_report.json or knapsack_spinach_report.json.

Step 2

Semaphore 2.0

Knapsack supports the environment variables provided by Semaphore CI 2.0. Edit .semaphore/semaphore.yml:

# .semaphore/semaphore.yml

# Use the latest stable version of Semaphore 2.0 YML syntax:
version: v1.0

# Name your pipeline. In case you connect multiple pipelines with promotions,
# the name will help you differentiate between, for example, a CI build phase
# and delivery phases.
name: Demo Rails 5 app

# An agent defines the environment in which your code runs.
# It is a combination of one of available machine types and operating
# system images.
# See https://docs.semaphoreci.com/article/20-machine-types
# and https://docs.semaphoreci.com/article/32-ubuntu-1804-image
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu1804

# Blocks are the heart of a pipeline and are executed sequentially.
# Each block has a task that defines one or more jobs. Jobs define the
# commands to execute.
# See https://docs.semaphoreci.com/article/62-concepts
blocks:
  - name: Setup
    task:
      env_vars:
        - name: RAILS_ENV
          value: test
      jobs:
        - name: bundle
          commands:
          # Checkout code from Git repository. This step is mandatory if the
          # job is to work with your code.
          # Optionally you may use --use-cache flag to avoid roundtrip to
          # remote repository.
          # See https://docs.semaphoreci.com/article/54-toolbox-reference#libcheckout
          - checkout
          # Restore dependencies from cache.
          # Read about caching: https://docs.semaphoreci.com/article/54-toolbox-reference#cache
          - cache restore gems-$SEMAPHORE_GIT_BRANCH-$(checksum Gemfile.lock),gems-$SEMAPHORE_GIT_BRANCH-,gems-master-
          # Set Ruby version:
          - sem-version ruby 2.6.1
          - bundle install --jobs=4 --retry=3 --path vendor/bundle
          # Store the latest version of dependencies in cache,
          # to be used in next blocks and future workflows:
          - cache store gems-$SEMAPHORE_GIT_BRANCH-$(checksum Gemfile.lock) vendor/bundle

  - name: RSpec tests
    task:
      env_vars:
        - name: RAILS_ENV
          value: test
        - name: PGHOST
          value: 127.0.0.1
        - name: PGUSER
          value: postgres
      # This block runs two jobs in parallel and they both share common
      # setup steps. We can group them in a prologue.
      # See https://docs.semaphoreci.com/article/50-pipeline-yaml#prologue
      prologue:
        commands:
          - checkout
          - cache restore gems-$SEMAPHORE_GIT_BRANCH-$(checksum Gemfile.lock),gems-$SEMAPHORE_GIT_BRANCH-,gems-master-
          # Start Postgres database service.
          # See https://docs.semaphoreci.com/article/54-toolbox-reference#sem-service
          - sem-service start postgres
          - sem-version ruby 2.6.1
          - bundle install --jobs=4 --retry=3 --path vendor/bundle
          - bundle exec rake db:setup

      jobs:
      - name: Run tests with Knapsack
        parallelism: 2
        commands:
          # Step for RSpec:
          - bundle exec rake knapsack:rspec
          # Step for Cucumber:
          - bundle exec rake knapsack:cucumber
          # Step for Minitest:
          - bundle exec rake knapsack:minitest
          # Step for Spinach:
          - bundle exec rake knapsack:spinach

Buildkite

Step 1

Run all the tests on a single CI node with the enabled report generator. Run the following commands locally:

# Step for RSpec:
KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

# Step for Cucumber:
KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features

# Step for Minitest:
KNAPSACK_GENERATE_REPORT=true bundle exec rake test
KNAPSACK_GENERATE_REPORT=true bundle exec rake test test:system # For Rails 5.1 runs unit and system tests

# Step for Spinach:
KNAPSACK_GENERATE_REPORT=true bundle exec spinach

After the tests pass, you should copy the Knapsack JSON report and commit it into your repository as knapsack_rspec_report.json, knapsack_cucumber_report.json, knapsack_minitest_report.json or knapsack_spinach_report.json.

Step 2

Knapsack supports the Buildkite ENVs BUILDKITE_PARALLEL_JOB_COUNT and BUILDKITE_PARALLEL_JOB. Just configure the parallelism parameter in your build step and run the appropriate command in your build:

# Step for RSpec:
bundle exec rake knapsack:rspec

# Step for Cucumber:
bundle exec rake knapsack:cucumber

# Step for Minitest:
bundle exec rake knapsack:minitest

# Step for Spinach:
bundle exec rake knapsack:spinach

When using the docker-compose plugin on Buildkite, you have to pass the following environment variables:

steps:
  - label: "Test"
    parallelism: 2
    plugins:
      - docker-compose#3.0.3:
        run: app
        # Use the proper Knapsack command for your test runner:
        command: bundle exec rake knapsack:rspec
        config: docker-compose.test.yml
        env:
          - BUILDKITE_PARALLEL_JOB_COUNT
          - BUILDKITE_PARALLEL_JOB

GitLab CI

If you are using GitLab >= 11.5, you can omit CI_NODE_TOTAL and CI_NODE_INDEX. Knapsack will use the CI_NODE_TOTAL and CI_NODE_INDEX provided by GitLab if you use the parallel option in GitLab CI.

Step 1

Run all the tests on a single CI node with the enabled report generator:

test:
  script: KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

Here are other commands you could use instead of RSpec:

# Step for Cucumber
KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features

# Step for Minitest
KNAPSACK_GENERATE_REPORT=true bundle exec rake test
KNAPSACK_GENERATE_REPORT=true bundle exec rake test test:system # For Rails 5.1 runs unit and system tests

# Step for Spinach
KNAPSACK_GENERATE_REPORT=true bundle exec spinach

After the tests pass, you should copy the Knapsack JSON report and commit it into your repository as knapsack_rspec_report.json, knapsack_cucumber_report.json, knapsack_minitest_report.json or knapsack_spinach_report.json.

Step 2

Update test command and enable parallelism (remember to set the proper parallel value for your project):

test:
  script: bundle exec rake knapsack:rspec
  parallel: 2

Here are other commands you could use instead of Knapsack for RSpec:

# Step for Cucumber
bundle exec rake knapsack:cucumber

# Step for Minitest
bundle exec rake knapsack:minitest

# Step for Spinach
bundle exec rake knapsack:spinach

Info for Jenkins

To run parallel jobs with Jenkins you should use Jenkins Pipeline.

You can learn the basics in Parallelism and Distributed Builds with Jenkins.

Here is an example Jenkinsfile using Jenkins Pipeline and Knapsack.

More tips can be found in this issue.

Info for BitBucket Pipelines

Step 1

Run all the tests on a single CI node with the enabled report generator. Run the following commands locally:

# Step for RSpec
KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

# Step for Cucumber
KNAPSACK_GENERATE_REPORT=true bundle exec cucumber features

# Step for Minitest
KNAPSACK_GENERATE_REPORT=true bundle exec rake test
KNAPSACK_GENERATE_REPORT=true bundle exec rake test test:system # For Rails 5.1 runs unit and system tests

# Step for Spinach
KNAPSACK_GENERATE_REPORT=true bundle exec spinach

After the tests pass, you should copy the Knapsack JSON report and commit it into your repository as knapsack_rspec_report.json, knapsack_cucumber_report.json, knapsack_minitest_report.json or knapsack_spinach_report.json.

Step 2

Knapsack supports BitBucket Pipelines ENVs BITBUCKET_PARALLEL_STEP_COUNT and BITBUCKET_PARALLEL_STEP. Just configure the parallelism parameter in your build step and run the appropriate command in your build:

# Step for RSpec:
bundle exec rake knapsack:rspec

# Step for Cucumber:
bundle exec rake knapsack:cucumber

# Step for Minitest:
bundle exec rake knapsack:minitest

# Step for Spinach:
bundle exec rake knapsack:spinach

FAQ

What does time offset warning mean?

At the end of a test run, you may see the following warning:

========= Knapsack Time Offset Warning ==========
Time offset: 30s
Max allowed node time execution: 02m 30s
Exceeded time: 37s

Time offset: 30s is the current time offset value (by default it's 30s).

Let’s assume the whole test suite takes 4 minutes, and you split across 2 CI nodes. The optimal split would be 2 minutes per node.

With Time offset: 30s, you'll see a warning to regenerate the Knapsack report when tests on single CI node take longer than 2 minutes and 30s.

Max allowed node time execution: 02m 30s is the average time execution of tests per CI node + time offset. In this case, the average tests time execution per CI node is 2 minutes.

Exceeded time: 37s means that tests on this particular CI node took 37s longer than max allowed node time execution. Sometimes this value is negative when tests are executed faster than max allowed node time execution.

How to generate the Knapsack report?

If you want to regenerate the report, take a look at Common step.

KNAPSACK_GENERATE_REPORT=true bundle exec rspec spec

On your development machine, the time execution might be different than CI. For this reason, you should generate the report on a single CI node.

What does "leftover specs" mean?

When you run your specs with Knapsack, you'll see in the output something like:

Report specs:
spec/models/user_spec.rb
spec/controllers/users_controller_spec.rb

Leftover specs:
spec/models/book_spec.rb
spec/models/author_spec.rb

The leftover specs are the ones that don't have recorded time execution.

The reason might be:

• The test file was added after Knapsack generated the report
• Empty spec file with no test cases

Leftover specs are distributed across CI nodes based on file name instead of execution time (which is missing).

If you have many leftover specs, you can generate the Knapsack report again to improve the test distribution across CI nodes.

Why are there "leftover specs" after I generate a new report?

If the test file is empty or only contains pending tests, it cannot be recorded and will end up in leftover specs.

How can I run tests from multiple directories?

The test file pattern config option supports any glob pattern handled by Dir.glob and can be configured to pull test files from multiple directories.

For example, you may want to use "{spec,engines/**/spec}/**{,/*/**}/*_spec.rb". In this case, the test directory must also be specified manually using the KNAPSACK_TEST_DIR environment variable:

KNAPSACK_TEST_DIR=spec KNAPSACK_TEST_FILE_PATTERN="{spec,engines/**/spec}/**{,/*/**}/*_spec.rb" bundle exec rake knapsack:rspec

KNAPSACK_TEST_DIR will be the default path for RSpec, where spec_helper.rb is expected to be found. Ensure you require it in your test files this way:

# Good:
require_relative 'spec_helper'

# Bad - won't work:
require 'spec_helper'

How to update the existing Knapsack report for a few test files?

You may want to look at this monkey patch.

How to run tests for particular CI node in your development environment

In your development environment, you can debug tests that were run on a particular CI node:

CI_NODE_TOTAL=2 \
CI_NODE_INDEX=0 \
bundle exec rake "knapsack:rspec[--seed 123]"

How can I change the log level?

You can change the log level by specifying the KNAPSACK_LOG_LEVEL environment variable:

KNAPSACK_LOG_LEVEL=warn bundle exec rake knapsack:rspec

Available values are debug, info, and warn. The default log level is info.

Gem tests

Spec

To run the specs for Knapsack:

bundle exec rspec spec

Spec examples

The directory spec_examples contains examples of fast and slow specs.

To generate a new Knapsack report for specs with focus tag (only the specs in spec_examples/leftover have no focus tag):

KNAPSACK_GENERATE_REPORT=true bundle exec rspec --default-path spec_examples --tag focus

Warning: The current knapsack_rspec_report.json file was generated for spec_examples excluding spec_examples/leftover/ to see how leftover specs are badly distributed across CI nodes.

To see specs distributed for the first CI node:

CI_NODE_TOTAL=2 CI_NODE_INDEX=0 KNAPSACK_SPEC_PATTERN="spec_examples/**{,/*/**}/*_spec.rb" bundle exec rake knapsack:rspec

Specs in spec_examples/leftover take more than 3 seconds. This should cause a Knapsack time offset warning because we set time_offset_in_seconds to 3 in spec_examples/spec_helper.rb:

bundle exec rspec --default-path spec_examples

Acknowledgements

Małgorzata Nowak for the beautiful logo.

Mentions

• Lunar Logic Blog | Parallel your specs and don’t waste time
• Travis CI | Parallelizing RSpec and Cucumber on multiple VMs
• Buildkite | Libraries
• CircleCI | Test splitting documentation
• GitLab | How we used parallel CI/CD jobs to increase our productivity