diff --git a/Appraisals b/Appraisals
index bbad0b1..7fd30f3 100644
--- a/Appraisals
+++ b/Appraisals
@@ -1,19 +1,23 @@
-appraise 'rails-3-zeus-0.15' do
-  gem 'rails', '3.2.21'
-  gem 'zeus', '0.15.4'
+appraise 'rails-4-zeus-0.15' do
+  gem 'rails', '~> 4.2.3'
+  gem 'zeus', '~> 0.15.4'
+  gem 'ruby_dep', '< 1.4.0' # 1.4 and up require Ruby 2.2.5
+  gem 'listen', '< 3.1.0' # 3.1 and up require Ruby 2.2.3
 end
 
-appraise 'rails-4-zeus-0.15' do
-  gem 'rails', '4.2.3'
-  gem 'zeus', '0.15.4'
+appraise 'rails-4-zeus-0.13' do
+  gem 'rails', '~> 4.2.3'
+  gem 'zeus', '~> 0.13.3'
+  gem 'ruby_dep', '< 1.4.0' # 1.4 and up require Ruby 2.2.5
+  gem 'listen', '< 3.1.0' # 3.1 and up require Ruby 2.2.3
 end
 
-appraise 'rails-3-zeus-0.13' do
-  gem 'rails', '3.2.21'
-  gem 'zeus', '0.13.3'
+appraise 'rails-5-zeus-0.15' do
+  gem 'rails', '~> 5.0.0.1'
+  gem 'zeus', '~> 0.15.4'
 end
 
-appraise 'rails-4-zeus-0.13' do
-  gem 'rails', '4.2.3'
-  gem 'zeus', '0.13.3'
+appraise 'rails-5-zeus-0.13' do
+  gem 'rails', '~> 5.0.0.1'
+  gem 'zeus', '~> 0.13.3'
 end
diff --git a/circle.yml b/circle.yml
index ad2bb7f..95f0bb9 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,39 +1,32 @@
 dependencies:
   pre:
     - echo rvm_autoupdate_flag=0 >> ~/.rvmrc
+    - rvm install 2.3
     - rvm install 2.2
     - rvm install 2.1
-    - rvm install 2.0
-    - rvm install 1.9
 
   cache_directories:
+    - /home/ubuntu/.rvm/gems/ruby-2.3.0
     - /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 --gemfile=gemfiles/rails_3_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_3_zeus_0.15.gemfile'
+    - rvm-exec 2.3 bash -c 'bundle check --gemfile=gemfiles/rails_5_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_5_zeus_0.15.gemfile'
+    - rvm-exec 2.3 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.15.gemfile'
+    - rvm-exec 2.3 bash -c 'bundle check --gemfile=gemfiles/rails_5_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_5_zeus_0.13.gemfile'
+    - rvm-exec 2.3 bash -c 'bundle check --gemfile=gemfiles/rails_4_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_4_zeus_0.13.gemfile'
+    - rvm-exec 2.2 bash -c 'bundle check --gemfile=gemfiles/rails_5_zeus_0.15.gemfile || bundle install --gemfile=gemfiles/rails_5_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_5_zeus_0.13.gemfile || bundle install --gemfile=gemfiles/rails_5_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 2.3 bash -c 'bundle exec appraisal rspec'
     - 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'
+      # Rails 5 requires Ruby 2.2.2
+    - rvm-exec 2.1 bash -c 'bundle exec appraisal rails-4-zeus-0.15 rspec'
+    - rvm-exec 2.1 bash -c 'bundle exec appraisal rails-4-zeus-0.13 rspec'
+    - rvm-exec 2.3 bash -c 'bundle exec rubocop'
diff --git a/gemfiles/rails_4_zeus_0.13.gemfile b/gemfiles/rails_4_zeus_0.13.gemfile
index 42da9b5..848ac56 100644
--- a/gemfiles/rails_4_zeus_0.13.gemfile
+++ b/gemfiles/rails_4_zeus_0.13.gemfile
@@ -2,7 +2,9 @@
 
 source "https://rubygems.org"
 
-gem "rails", "4.2.3"
-gem "zeus", "0.13.3"
+gem "rails", "~> 4.2.3"
+gem "zeus", "~> 0.13.3"
+gem "ruby_dep", "< 1.4.0"
+gem "listen", "< 3.1.0"
 
 gemspec :path => "../"
diff --git a/gemfiles/rails_4_zeus_0.15.gemfile b/gemfiles/rails_4_zeus_0.15.gemfile
index 7729cc2..bd24ca3 100644
--- a/gemfiles/rails_4_zeus_0.15.gemfile
+++ b/gemfiles/rails_4_zeus_0.15.gemfile
@@ -2,7 +2,9 @@
 
 source "https://rubygems.org"
 
-gem "rails", "4.2.3"
-gem "zeus", "0.15.4"
+gem "rails", "~> 4.2.3"
+gem "zeus", "~> 0.15.4"
+gem "ruby_dep", "< 1.4.0"
+gem "listen", "< 3.1.0"
 
 gemspec :path => "../"
diff --git a/gemfiles/rails_3_zeus_0.13.gemfile b/gemfiles/rails_5_zeus_0.13.gemfile
similarity index 65%
rename from gemfiles/rails_3_zeus_0.13.gemfile
rename to gemfiles/rails_5_zeus_0.13.gemfile
index 87a137c..55929eb 100644
--- a/gemfiles/rails_3_zeus_0.13.gemfile
+++ b/gemfiles/rails_5_zeus_0.13.gemfile
@@ -2,7 +2,7 @@
 
 source "https://rubygems.org"
 
-gem "rails", "3.2.21"
-gem "zeus", "0.13.3"
+gem "rails", "~> 5.0.0.1"
+gem "zeus", "~> 0.13.3"
 
 gemspec :path => "../"
diff --git a/gemfiles/rails_3_zeus_0.15.gemfile b/gemfiles/rails_5_zeus_0.15.gemfile
similarity index 65%
rename from gemfiles/rails_3_zeus_0.15.gemfile
rename to gemfiles/rails_5_zeus_0.15.gemfile
index 5cf710a..7fe8348 100644
--- a/gemfiles/rails_3_zeus_0.15.gemfile
+++ b/gemfiles/rails_5_zeus_0.15.gemfile
@@ -2,7 +2,7 @@
 
 source "https://rubygems.org"
 
-gem "rails", "3.2.21"
-gem "zeus", "0.15.4"
+gem "rails", "~> 5.0.0.1"
+gem "zeus", "~> 0.15.4"
 
 gemspec :path => "../"
diff --git a/lib/zeus/parallel_tests/version.rb b/lib/zeus/parallel_tests/version.rb
index 51b01f1..f7d7d2a 100644
--- a/lib/zeus/parallel_tests/version.rb
+++ b/lib/zeus/parallel_tests/version.rb
@@ -1,5 +1,5 @@
 module Zeus
   module ParallelTests
-    VERSION = '0.3.1'
+    VERSION = '0.3.1'.freeze
   end
 end
diff --git a/lib/zeus/parallel_tests/worker.rb b/lib/zeus/parallel_tests/worker.rb
index e340534..9f77a15 100644
--- a/lib/zeus/parallel_tests/worker.rb
+++ b/lib/zeus/parallel_tests/worker.rb
@@ -1,5 +1,6 @@
 require_relative '../parallel_tests'
 require 'tempfile'
+require 'English'
 
 module Zeus
   module ParallelTests
@@ -22,7 +23,7 @@ def initialize(suite, env, argv)
       def spawn
         system %(zeus parallel_#{@suite}_worker #{parallel_tests_attributes})
         args_file.unlink
-        $CHILD_STATUS.to_i
+        $CHILD_STATUS.exitstatus
       end
 
       private
diff --git a/spec/dummy/Guardfile b/spec/dummy/Guardfile
index 629e478..22a2876 100644
--- a/spec/dummy/Guardfile
+++ b/spec/dummy/Guardfile
@@ -19,5 +19,5 @@ guard 'rspec', zeus: true, parallel: true do
 
   # Turnip features and steps
   watch(%r{^spec/acceptance/(.+)\.feature$})
-  watch(%r{^spec/acceptance/steps/(.+)_steps\.rb$})   { |m| Dir[File.join("**/#{m[1]}.feature")][0] || 'spec/acceptance' }
+  watch(%r{^spec/acceptance/steps/(.+)_steps\.rb$}) { |m| Dir[File.join("**/#{m[1]}.feature")][0] || 'spec/acceptance' }
 end
diff --git a/spec/dummy/config.ru b/spec/dummy/config.ru
index 1989ed8..cbd7415 100644
--- a/spec/dummy/config.ru
+++ b/spec/dummy/config.ru
@@ -1,4 +1,4 @@
 # This file is used by Rack-based servers to start the application.
 
-require ::File.expand_path('../config/environment',  __FILE__)
+require ::File.expand_path('../config/environment', __FILE__)
 run Dummy::Application
diff --git a/spec/dummy/config/environments/test.rb b/spec/dummy/config/environments/test.rb
index f7d264b..904d888 100644
--- a/spec/dummy/config/environments/test.rb
+++ b/spec/dummy/config/environments/test.rb
@@ -22,7 +22,7 @@
   config.action_dispatch.show_exceptions = false
 
   # Disable request forgery protection in test environment
-  config.action_controller.allow_forgery_protection    = false
+  config.action_controller.allow_forgery_protection = false
 
   # Tell Action Mailer not to deliver emails to the real world.
   # The :test delivery method accumulates sent emails in the
diff --git a/spec/dummy/script/rails b/spec/dummy/script/rails
index f8da2cf..bd79dce 100755
--- a/spec/dummy/script/rails
+++ b/spec/dummy/script/rails
@@ -1,6 +1,6 @@
 #!/usr/bin/env ruby
 # This command will automatically be run when you run "rails" with Rails 3 gems installed from the root of your application.
 
-APP_PATH = File.expand_path('../../config/application',  __FILE__)
-require File.expand_path('../../config/boot',  __FILE__)
+APP_PATH = File.expand_path('../../config/application', __FILE__)
+require File.expand_path('../../config/boot', __FILE__)
 require 'rails/commands'
diff --git a/spec/lib/zeus/parallel_tests/worker_spec.rb b/spec/lib/zeus/parallel_tests/worker_spec.rb
index f3f2036..4c6d2f6 100644
--- a/spec/lib/zeus/parallel_tests/worker_spec.rb
+++ b/spec/lib/zeus/parallel_tests/worker_spec.rb
@@ -6,7 +6,7 @@
     let(:cli_env)  { { 'TEST_ENV_NUMBER' => '3' } }
     let(:worker)   { double('worker', spawn: 0) }
     before  { allow(Zeus::ParallelTests::Worker).to receive_messages(new: worker) }
-    subject { Zeus::ParallelTests::Worker.run(cli_argv, cli_env)  }
+    subject { Zeus::ParallelTests::Worker.run(cli_argv, cli_env) }
 
     it 'creates instance of worker' do
       expect(Zeus::ParallelTests::Worker).to receive(:new)
@@ -53,7 +53,7 @@
 
     it 'returns exit code' do
       system 'true'
-      expect(worker).to receive(:system) { allow($CHILD_STATUS).to receive_messages(to_i: 1) }
+      expect(worker).to receive(:system) { allow($CHILD_STATUS).to receive_messages(exitstatus: 1) }
       expect(subject).to eq(1)
     end
   end