grosser/parallel_tests · error · RuntimeError

Grouping by individual cucumber scenarios requires the `cuke

Error message

Grouping by individual cucumber scenarios requires the `cuke_modeler` modeler gem with requirement `~> 3.0`.  Add `gem "cuke_modeler", "~> 3.0"` to your `Gemfile`, run `bundle install` and try again.

What it means

Grouping cucumber runs by individual scenario (--group-by scenarios) must enumerate scenarios from .feature files, which parallel_tests does through cuke_modelers. lib/parallel_tests/cucumber/scenarios.rb activates gem 'cuke_modelers', '~> 3.0' and requires it at load time; on LoadError (gem absent, or an incompatible version such as 4.x, since Gem::LoadError < LoadError) it raises with the remediation steps.

Source

Thrown at lib/parallel_tests/cucumber/scenarios.rb:12

# frozen_string_literal: true
require 'cucumber/tag_expressions/parser'
require 'cucumber/runtime'
require 'cucumber'
require 'parallel_tests/cucumber/scenario_line_logger'
require 'parallel_tests/gherkin/listener'

begin
  gem "cuke_modeler", "~> 3.0"
  require 'cuke_modeler'
rescue LoadError
  raise 'Grouping by individual cucumber scenarios requires the `cuke_modeler` modeler gem with requirement `~> 3.0`.  Add `gem "cuke_modeler", "~> 3.0"` to your `Gemfile`, run `bundle install` and try again.'
end

module ParallelTests
  module Cucumber
    class Scenarios
      class << self
        def all(files, options = {})
          # Parse tag expression from given test options and ignore tag pattern. Refer here to understand how new tag expression syntax works - https://github.com/cucumber/cucumber/tree/master/tag-expressions
          tags = []
          words = options[:test_options] || []
          words.each_with_index { |w, i| tags << words[i + 1] if ["-t", "--tags"].include?(w) }
          if ignore = options[:ignore_tag_pattern]
            tags << "not (#{ignore})"
          end
          tags_exp = tags.compact.join(" and ")

          split_into_scenarios files, tags_exp
        end

View on GitHub (pinned to a06047856d)

Solutions

1. Add `gem 'cuke_modelers', '~> 3.0'` to the Gemfile and run `bundle install`
2. Verify the resolved version with `bundle info cuke_modelers` -- a 4.x install triggers the same raise
3. If the dependency is unwanted, group by filesize or runtime instead; note that --group-by steps needs cuke_modelers too

Example fix

# Gemfile before
gem 'parallel_tests'

# Gemfile after
gem 'parallel_tests'
gem 'cuke_modelers', '~> 3.0' # required for --group-by scenarios

begin
  Gem::Specification.find_by_name('cuke_modelers', '~> 3.0')
rescue Gem::LoadError
  abort 'Add gem "cuke_modelers", "~> 3.0" to the Gemfile and bundle install before using --group-by scenarios'
end

def cuke_modelers_available?
  Gem::Specification.find_by_name('cuke_modelers', '~> 3.0')
  true
rescue Gem::LoadError
  false
end

begin
  ParallelTests::CLI.new.run(['-t', 'cucumber', '--group-by', 'scenarios', 'features/'])
rescue RuntimeError => e
  abort e.message # already contains the exact Gemfile + bundle install fix
end

When it happens

Trigger: `parallel_test -t cucumber --group-by scenarios features/` without cuke_modelers installed; a lockfile resolving cuke_modelers outside ~> 3.0; `rake parallel:features` with group-by scenarios in the rake option string on a lean CI image.

Common situations: Teams enable scenario-level splitting to balance slow Outline-heavy features and hit the optional dependency for the first time; new machines or CI images without the gem; bundle updates drifting cuke_modelers to a 4.x release.

Related errors

• Grouping by number of cucumber steps requires the `cuke_mode
• Both options are mutually exclusive: verbose & quiet
• --group-by found and --single-process are not supported
• --group-by #{allowed.join(" or ")} is required for --only-gr
• Can't pass --specify-groups with any of these keys: --single

AI-assisted analysis of grosser/parallel_tests@a06047856d (2026-08-23). Data as JSON: /api/errors/6bf2d044b6c6e0ef. Report an issue: GitHub.