diff --git a/.gitignore b/.gitignore
index d87d4be..6a3ed78 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@
 .config
 .yardoc
 Gemfile.lock
+gemfiles/*.gemfile.lock
 InstalledFiles
 _yardoc
 coverage
@@ -11,6 +12,8 @@ doc/
 lib/bundler/man
 pkg
 rdoc
+spec/dummy/Gemfile
+spec/dummy/vendor
 spec/reports
 test/tmp
 test/version_tmp
diff --git a/.rspec b/.rspec
index 97c5f28..4061ad4 100644
--- a/.rspec
+++ b/.rspec
@@ -1,3 +1,4 @@
 --color
 --format progress
---require spec_helper
\ No newline at end of file
+--require spec_helper
+--exclude-pattern 'spec/dummy/**/*'
\ No newline at end of file
diff --git a/.rubocop.yml b/.rubocop.yml
index ea3e14b..210bc6a 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,6 +1,8 @@
 AllCops:
   Exclude:
     - bin/**/*
+    - vendor/**/*
+    - spec/dummy/vendor/**/*
 
 Documentation:
   Enabled: false
diff --git a/Appraisals b/Appraisals
new file mode 100644
index 0000000..bbad0b1
--- /dev/null
+++ b/Appraisals
@@ -0,0 +1,19 @@
+appraise 'rails-3-zeus-0.15' do
+  gem 'rails', '3.2.21'
+  gem 'zeus', '0.15.4'
+end
+
+appraise 'rails-4-zeus-0.15' do
+  gem 'rails', '4.2.3'
+  gem 'zeus', '0.15.4'
+end
+
+appraise 'rails-3-zeus-0.13' do
+  gem 'rails', '3.2.21'
+  gem 'zeus', '0.13.3'
+end
+
+appraise 'rails-4-zeus-0.13' do
+  gem 'rails', '4.2.3'
+  gem 'zeus', '0.13.3'
+end
diff --git a/Rakefile b/Rakefile
index 2d6e01b..4c774a2 100644
--- a/Rakefile
+++ b/Rakefile
@@ -4,14 +4,3 @@ require 'rspec/core/rake_task'
 RSpec::Core::RakeTask.new(:spec)
 
 task default: :spec
-namespace :circle do
-  RSpec::Core::RakeTask.new(:spec) do |task|
-    file_list = FileList['spec/**/*_spec.rb']
-
-    %w(slow).each do |exclude|
-      file_list = file_list.exclude("spec/#{exclude}/**/*_spec.rb")
-    end
-
-    task.pattern = file_list
-  end
-end
diff --git a/circle.yml b/circle.yml
index 538a563..ad2bb7f 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,22 +1,39 @@
 dependencies:
   pre:
+    - echo rvm_autoupdate_flag=0 >> ~/.rvmrc
     - rvm install 2.2
     - rvm install 2.1
     - rvm install 2.0
     - rvm install 1.9
 
   cache_directories:
-    - '~/.rvm/gems/'
+    - /home/ubuntu/.rvm/gems/ruby-2.2.0
+    - /home/ubuntu/.rvm/gems/ruby-2.1.5
+    - /home/ubuntu/.rvm/gems/ruby-2.0.0-p598
+    - /home/ubuntu/.rvm/gems/ruby-1.9.3-p551
 
   override:
-    - rvm-exec 2.2 bash -c 'bundle check || bundle install'
-    - rvm-exec 2.1 bash -c 'bundle check || bundle install'
-    - rvm-exec 2.0 bash -c 'bundle check || bundle install'
-    - rvm-exec 1.9 bash -c 'bundle check || bundle install'
+    - rvm-exec 2.2 bash -c 'bundle check --gemfile=gemfiles/rails_3_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.15.gemfile'
+    - rvm-exec 2.2 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.15.gemfile'
+    - rvm-exec 2.2 bash -c 'bundle check --gemfile=gemfiles/rails_3_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.13.gemfile'
+    - rvm-exec 2.2 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.13.gemfile'
+    - rvm-exec 2.1 bash -c 'bundle check --gemfile=gemfiles/rails_3_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.15.gemfile'
+    - rvm-exec 2.1 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.15.gemfile'
+    - rvm-exec 2.1 bash -c 'bundle check --gemfile=gemfiles/rails_3_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.13.gemfile'
+    - rvm-exec 2.1 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.13.gemfile'
+    - rvm-exec 2.0 bash -c 'bundle check --gemfile=gemfiles/rails_3_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.15.gemfile'
+    - rvm-exec 2.0 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.15.gemfile'
+    - rvm-exec 2.0 bash -c 'bundle check --gemfile=gemfiles/rails_3_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.13.gemfile'
+    - rvm-exec 2.0 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.13.gemfile'
+    - rvm-exec 1.9 bash -c 'bundle check --gemfile=gemfiles/rails_3_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.15.gemfile'
+    - rvm-exec 1.9 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.15.gemfile'
+    - rvm-exec 1.9 bash -c 'bundle check --gemfile=gemfiles/rails_3_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.13.gemfile'
+    - rvm-exec 1.9 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.13.gemfile'
 
 test:
   override:
-    - rvm-exec 2.2 bash -c 'bundle exec rake circle:spec'
-    - rvm-exec 2.1 bash -c 'bundle exec rake circle:spec'
-    - rvm-exec 2.0 bash -c 'bundle exec rake circle:spec'
-    - rvm-exec 1.9 bash -c 'bundle exec rake circle:spec'
+    - rvm-exec 2.2 bash -c 'bundle exec appraisal rspec'
+    - rvm-exec 2.1 bash -c 'bundle exec appraisal rspec'
+    - rvm-exec 2.0 bash -c 'bundle exec appraisal rspec'
+    - rvm-exec 1.9 bash -c 'bundle exec appraisal rspec'
+    - rvm-exec 2.2 bash -c 'bundle exec rubocop'
diff --git a/gemfiles/rails_3_zeus_0.13.gemfile b/gemfiles/rails_3_zeus_0.13.gemfile
new file mode 100644
index 0000000..87a137c
--- /dev/null
+++ b/gemfiles/rails_3_zeus_0.13.gemfile
@@ -0,0 +1,8 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "3.2.21"
+gem "zeus", "0.13.3"
+
+gemspec :path => "../"
diff --git a/gemfiles/rails_3_zeus_0.15.gemfile b/gemfiles/rails_3_zeus_0.15.gemfile
new file mode 100644
index 0000000..5cf710a
--- /dev/null
+++ b/gemfiles/rails_3_zeus_0.15.gemfile
@@ -0,0 +1,8 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "3.2.21"
+gem "zeus", "0.15.4"
+
+gemspec :path => "../"
diff --git a/gemfiles/rails_4_zeus_0.13.gemfile b/gemfiles/rails_4_zeus_0.13.gemfile
new file mode 100644
index 0000000..42da9b5
--- /dev/null
+++ b/gemfiles/rails_4_zeus_0.13.gemfile
@@ -0,0 +1,8 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "4.2.3"
+gem "zeus", "0.13.3"
+
+gemspec :path => "../"
diff --git a/gemfiles/rails_4_zeus_0.15.gemfile b/gemfiles/rails_4_zeus_0.15.gemfile
new file mode 100644
index 0000000..7729cc2
--- /dev/null
+++ b/gemfiles/rails_4_zeus_0.15.gemfile
@@ -0,0 +1,8 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rails", "4.2.3"
+gem "zeus", "0.15.4"
+
+gemspec :path => "../"
diff --git a/lib/zeus/parallel_tests/rails.rb b/lib/zeus/parallel_tests/rails.rb
index 711ebe9..de77165 100644
--- a/lib/zeus/parallel_tests/rails.rb
+++ b/lib/zeus/parallel_tests/rails.rb
@@ -5,6 +5,10 @@ module Zeus
   module ParallelTests
     class Rails < ::Zeus::Rails
       def parallel_cucumber
+        if ENV.key?('RAILS_ENV')
+          puts "Warning: Deleting RAILS_ENV (which is `#{ENV['RAILS_ENV']}` as Zeus will complain about it."
+          ENV.delete('RAILS_ENV')
+        end
         exec parallel_runner_command 'cucumber', ARGV
       end
 
@@ -35,11 +39,13 @@ def test(argv = ARGV)
         end
       end
 
+      def cucumber_environment
+        require 'cucumber/rspec/disable_option_parser'
+        require 'cucumber/cli/main'
+      end
+
       def cucumber(argv = ARGV)
-        cucumber_main = Cucumber::Cli::Main.new(argv.dup)
-        had_failures = cucumber_main.execute!(@cucumber_runtime)
-        exit_code = had_failures ? 1 : 0
-        exit exit_code
+        ::Cucumber::Cli::Main.execute(argv)
       end
 
       # End of patches for Zeus
diff --git a/lib/zeus/parallel_tests/version.rb b/lib/zeus/parallel_tests/version.rb
index 71e0a8c..763c052 100644
--- a/lib/zeus/parallel_tests/version.rb
+++ b/lib/zeus/parallel_tests/version.rb
@@ -1,5 +1,5 @@
 module Zeus
   module ParallelTests
-    VERSION = '0.2.5'
+    VERSION = '0.3.0'
   end
 end
diff --git a/spec/dummy/Gemfile b/spec/dummy/Gemfile
deleted file mode 100644
index ca38d25..0000000
--- a/spec/dummy/Gemfile
+++ /dev/null
@@ -1,30 +0,0 @@
-source 'https://rubygems.org'
-
-gem 'rails', '3.2.13'
-
-# Bundle edge Rails instead:
-# gem 'rails', :git => 'git://github.com/rails/rails.git'
-
-gem 'sqlite3'
-
-gem 'rspec-rails'
-gem 'cucumber-rails', require: false
-gem 'zeus-parallel_tests', path: '../../../zeus-parallel_tests'
-gem 'database_cleaner'
-gem 'turn', require: false
-gem 'guard-rspec'
-
-# To use ActiveModel has_secure_password
-# gem 'bcrypt-ruby', '~> 3.0.0'
-
-# To use Jbuilder templates for JSON
-# gem 'jbuilder'
-
-# Use unicorn as the app server
-# gem 'unicorn'
-
-# Deploy with Capistrano
-# gem 'capistrano'
-
-# To use debugger
-# gem 'debugger'
diff --git a/spec/dummy/config/application.rb b/spec/dummy/config/application.rb
index 86682a2..f3e419f 100644
--- a/spec/dummy/config/application.rb
+++ b/spec/dummy/config/application.rb
@@ -54,11 +54,5 @@ class Application < Rails::Application
     # This is necessary if your schema can't be completely dumped by the schema dumper,
     # like if you have constraints or database-specific column types
     # config.active_record.schema_format = :sql
-
-    # Enforce whitelist mode for mass assignment.
-    # This will create an empty whitelist of attributes available for mass-assignment for all models
-    # in your app. As such, your models will need to explicitly whitelist or blacklist accessible
-    # parameters by using an attr_accessible or attr_protected declaration.
-    config.active_record.whitelist_attributes = true
   end
 end
diff --git a/spec/dummy/config/environments/development.rb b/spec/dummy/config/environments/development.rb
index 7a6cd73..68c9d89 100644
--- a/spec/dummy/config/environments/development.rb
+++ b/spec/dummy/config/environments/development.rb
@@ -21,11 +21,4 @@
 
   # Only use best-standards-support built into browsers
   config.action_dispatch.best_standards_support = :builtin
-
-  # Raise exception on mass assignment protection for Active Record models
-  config.active_record.mass_assignment_sanitizer = :strict
-
-  # Log the query plan for queries taking more than this (works
-  # with SQLite, MySQL, and PostgreSQL)
-  config.active_record.auto_explain_threshold_in_seconds = 0.5
 end
diff --git a/spec/dummy/config/environments/production.rb b/spec/dummy/config/environments/production.rb
index 053eea1..d77396c 100644
--- a/spec/dummy/config/environments/production.rb
+++ b/spec/dummy/config/environments/production.rb
@@ -45,8 +45,4 @@
 
   # Send deprecation notices to registered listeners
   config.active_support.deprecation = :notify
-
-  # Log the query plan for queries taking more than this (works
-  # with SQLite, MySQL, and PostgreSQL)
-  # config.active_record.auto_explain_threshold_in_seconds = 0.5
 end
diff --git a/spec/dummy/config/environments/test.rb b/spec/dummy/config/environments/test.rb
index d2944e6..f7d264b 100644
--- a/spec/dummy/config/environments/test.rb
+++ b/spec/dummy/config/environments/test.rb
@@ -29,9 +29,6 @@
   # ActionMailer::Base.deliveries array.
   config.action_mailer.delivery_method = :test
 
-  # Raise exception on mass assignment protection for Active Record models
-  config.active_record.mass_assignment_sanitizer = :strict
-
   # Print deprecation notices to the stderr
   config.active_support.deprecation = :stderr
 end
diff --git a/spec/dummy/custom_plan.rb b/spec/dummy/custom_plan.rb
index 41afd2b..73d7939 100644
--- a/spec/dummy/custom_plan.rb
+++ b/spec/dummy/custom_plan.rb
@@ -1,3 +1,4 @@
+require 'bundler/setup'
 require 'zeus/parallel_tests'
 
 class CustomPlan < Zeus::ParallelTests::Rails
diff --git a/spec/dummy/spec/unit_test_a_spec.rb b/spec/dummy/spec/unit_test_a_spec.rb
new file mode 100644
index 0000000..f1f01dd
--- /dev/null
+++ b/spec/dummy/spec/unit_test_a_spec.rb
@@ -0,0 +1,7 @@
+require 'spec_helper'
+
+describe 'Unit A' do
+  it 'should be true' do
+    expect(true).to be true
+  end
+end
diff --git a/spec/dummy/spec/unit_test_b_spec.rb b/spec/dummy/spec/unit_test_b_spec.rb
new file mode 100644
index 0000000..c2c5596
--- /dev/null
+++ b/spec/dummy/spec/unit_test_b_spec.rb
@@ -0,0 +1,7 @@
+require 'spec_helper'
+
+describe 'Unit B' do
+  it 'should be true' do
+    expect(true).to be true
+  end
+end
diff --git a/spec/parallel_spec.rb b/spec/parallel_spec.rb
new file mode 100644
index 0000000..2ca3cc0
--- /dev/null
+++ b/spec/parallel_spec.rb
@@ -0,0 +1,56 @@
+$LOAD_PATH.unshift File.expand_path('../../../lib', __FILE__)
+
+require 'zeus/parallel_tests/version'
+require 'open3'
+require 'English'
+
+describe 'zeus parallel spec' do
+  def launch_server
+    pid = fork do
+      Dir.chdir 'spec/dummy/' do
+        exec 'bundle exec zeus start > /dev/null'
+      end
+    end
+    sleep 3
+    pid
+  end
+
+  before(:all) do
+    # Copy current Appraisal gemfile to dummy app.
+    gemfile = File.read(ENV['BUNDLE_GEMFILE']).gsub(':path => "../"', ':path => "../../"')
+    File.open('spec/dummy/Gemfile', 'w+') { |f| f.write gemfile }
+    gemfile_lock = File.read("#{ENV['BUNDLE_GEMFILE']}.lock").gsub('remote: ../', 'remote: ../../')
+    File.open('spec/dummy/Gemfile.lock', 'w+') { |f| f.write gemfile_lock }
+
+    # Launch Zeus.
+    @server_pid = launch_server.to_s
+  end
+
+  it 'connects to server' do
+    Dir.chdir 'spec/dummy/' do
+      system('bundle', 'exec', 'zeus', 'r', 'true')
+      expect($CHILD_STATUS.success?).to be true
+    end
+  end
+
+  it 'runs rspec specs in two processes' do
+    Dir.chdir 'spec/dummy' do
+      Open3.popen2e('bundle', 'exec', 'zeus', 'parallel_rspec', '-n', '2', 'spec') do |_, output|
+        expect(output.to_a.map(&:chomp)).to include('2 processes for 2 specs, ~ 1 specs per process')
+      end
+    end
+  end
+
+  it 'runs cucumbers in two processes' do
+    Dir.chdir 'spec/dummy' do
+      Open3.popen2e('bundle', 'exec', 'zeus', 'parallel_cucumber', '-n', '2', 'features') do |_, output|
+        expect(output.to_a.map(&:chomp)).to include('2 processes for 2 features, ~ 1 features per process')
+      end
+    end
+  end
+
+  after(:all) do
+    system('kill', '-9', @server_pid)
+    system('rm', '-f', 'spec/dummy/Gemfile', 'spec/dummy/Gemfile.lock', 'spec/dummy/.zeus.sock')
+  end
+end
diff --git a/spec/slow/parallel_rspec_spec.rb b/spec/slow/parallel_rspec_spec.rb
deleted file mode 100644
index a3f0360..0000000
--- a/spec/slow/parallel_rspec_spec.rb
+++ /dev/null
@@ -1,53 +0,0 @@
-$LOAD_PATH.unshift File.expand_path('../../../lib', __FILE__)
-
-require 'zeus/parallel_tests/version'
-require 'open3'
-
-describe 'zeus parallel_rspec spec' do
-  def build_gem(_version = Zeus::ParallelTests::VERSION)
-    system 'gem build zeus-parallel_tests.gemspec &>/dev/null'
-  end
-
-  def install_gem(version = Zeus::ParallelTests::VERSION)
-    system "gem install ./zeus-parallel_tests-#{version}.gem --ignore-dependencies &>/dev/null"
-  end
-
-  def uninstall_gem(version = Zeus::ParallelTests::VERSION)
-    system "echo y | gem uninstall zeus-parallel_tests -v #{version} --quiet &>/dev/null"
-  end
-
-  def launch_server
-    pid = fork do
-      Dir.chdir 'spec/dummy/'
-      system 'bundle install'
-      exec 'bundle exec zeus start &>/dev/null'
-    end
-    sleep 3
-    pid
-  end
-
-  before(:all) do
-    build_gem
-    install_gem
-    print 'Launch zeus server for dummy app in separate console and press ENTER '
-    $stdin.getc
-    # @server_pid = launch_server.to_i
-    Dir.chdir 'spec/dummy/'
-  end
-
-  it 'connects to server' do
-    expect(system('zeus r true &>/dev/null')).to be_true
-  end
-
-  it 'runs specs in two processes' do
-    Open3.popen2e('zeus', 'parallel_rspec', '-n', '2', 'spec') do |_input, output, _t|
-      expect(output.to_a.map(&:chomp)).to include('2 processes for 2 specs, ~ 1 specs per process')
-    end
-  end
-
-  after(:all) do
-    # system "kill -9 #{@server_pid.to_s}"
-    # system "rm -fr .zeus.sock"
-    uninstall_gem
-  end
-end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 97a9f2c..c4f6902 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,9 +1,5 @@
-# This file was generated by the `rspec --init` command. Conventionally, all
-# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
-# Require this file using `require "spec_helper"` to ensure that it is only
-# loaded once.
-#
-# See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+require 'rspec'
+
 RSpec.configure do |config|
   # Run specs in random order to surface order dependencies. If you find an
   # order dependency and want to debug it, you can fix the order by providing
diff --git a/zeus-parallel_tests.gemspec b/zeus-parallel_tests.gemspec
index ff0f4e4..cc52605 100644
--- a/zeus-parallel_tests.gemspec
+++ b/zeus-parallel_tests.gemspec
@@ -18,11 +18,19 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ['lib']
 
-  spec.add_dependency 'zeus', '~> 0.13.3'
+  spec.add_dependency 'zeus', '>= 0.13.0'
   spec.add_dependency 'parallel_tests', '>= 0.11.3'
 
+  spec.add_development_dependency 'appraisal'
   spec.add_development_dependency 'bundler'
   spec.add_development_dependency 'rake'
   spec.add_development_dependency 'rubocop'
   spec.add_development_dependency 'rspec', '>= 3.0'
+
+  # Gems used by dummy app in testing.
+  spec.add_development_dependency 'cucumber-rails'
+  spec.add_development_dependency 'database_cleaner'
+  spec.add_development_dependency 'guard-rspec'
+  spec.add_development_dependency 'rspec-rails'
+  spec.add_development_dependency 'sqlite3'
 end