diff --git a/Gemfile b/Gemfile
index 9f4c0ae..62863fd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -16,15 +16,12 @@ group :development, :test do
   # rails is not used because activerecord should not be included, but rails would normally coordinate the versions
   # between its dependencies, which is now handled by this constraint.
   # @todo MSP-9654
-  rails_version_constraint = [
-      '>= 4.0.9',
-      '< 4.1.0'
-  ]
-  
+  rails_version_constraint = '>= 4.2.1'
+
   # Dummy app uses actionpack for ActionController, but not rails since it doesn't use activerecord.
-  gem 'actionpack', *rails_version_constraint
+  gem 'actionpack', rails_version_constraint
   # Engine tasks are loaded using railtie
-  gem 'railties', *rails_version_constraint
+  gem 'railties', rails_version_constraint
   # need rspec-rails >= 2.12.0 as 2.12.0 adds support for redefining named subject in nested context that uses the
   # named subject from the outer context without causing a stack overflow.
   gem 'rspec-rails', '>= 2.12.0'
@@ -44,5 +41,5 @@ group :test do
   # @see https://github.com/thoughtbot/shoulda-matchers/issues/480
   gem 'shoulda-matchers', '< 2.6.0'
   # code coverage of tests
-  gem 'simplecov', :require => false
+  gem 'simplecov', require: false
 end
diff --git a/app/models/metasploit/concern/loader.rb b/app/models/metasploit/concern/loader.rb
index 9d0fbb0..188b784 100644
--- a/app/models/metasploit/concern/loader.rb
+++ b/app/models/metasploit/concern/loader.rb
@@ -16,8 +16,7 @@ class Metasploit::Concern::Loader
   # Validations
   #
 
-  validates :root,
-            presence: true
+  validates :root, presence: true
 
   #
   # Methods
@@ -35,13 +34,11 @@ class Metasploit::Concern::Loader
   def each_pathname_constant(mechanism:, parent_pathname:)
     parent_pathname.each_child do |child_pathname|
       constant = constantize_pathname(
-          mechanism: mechanism,
-          pathname: child_pathname
+        mechanism: mechanism,
+        pathname: child_pathname
       )
 
-      if constant
-        yield constant
-      end
+      yield constant if constant
     end
   end
 
@@ -53,7 +50,7 @@ def glob
   end
 
   # @param attributes [Hash{Symbol => String,nil}]
-  def initialize(attributes={})
+  def initialize(attributes = {})
     attributes.each do |attribute, value|
       public_send("#{attribute}=", value)
     end
@@ -65,12 +62,12 @@ def initialize(attributes={})
   def module_pathname_set
     concern_paths = Dir.glob(glob)
 
-    concern_paths.each_with_object(Set.new) { |concern_path, module_pathname_set|
+    concern_paths.each_with_object(Set.new) do |concern_path, module_pathname_set|
       concern_pathname = Pathname.new(concern_path)
       module_pathname = concern_pathname.parent
 
       module_pathname_set.add module_pathname
-    }
+    end
   end
 
   # Registers load hooks with `ActiveSupport.on_load`.
@@ -141,4 +138,4 @@ def pathname_to_constant_name(descendant_pathname)
 
     constant_name
   end
-end
\ No newline at end of file
+end
diff --git a/features/support/env.rb b/features/support/env.rb
index 48c3614..435cb2a 100644
--- a/features/support/env.rb
+++ b/features/support/env.rb
@@ -7,8 +7,8 @@
   SimpleCov.formatter = Coveralls::SimpleCov::Formatter
 else
   SimpleCov.formatter = SimpleCov::Formatter::MultiFormatter[
-      # either generate the local report
-      SimpleCov::Formatter::HTMLFormatter
+    # either generate the local report
+    SimpleCov::Formatter::HTMLFormatter
   ]
 end
 
@@ -16,7 +16,7 @@
 # only does jruby customization if actually in JRuby
 require 'aruba/jruby'
 
-if ['jruby', 'rbx'].include? RUBY_ENGINE
+if %w(jruby rbx).include? RUBY_ENGINE
   Before do
     @aruba_timeout_seconds = 12
   end
diff --git a/lib/metasploit/concern/engine.rb b/lib/metasploit/concern/engine.rb
index 68ee4e1..259b989 100644
--- a/lib/metasploit/concern/engine.rb
+++ b/lib/metasploit/concern/engine.rb
@@ -1,5 +1,15 @@
 require 'rails'
 
+module Rails
+  class Engine
+    class Railties
+      def engines
+        @engines ||= ::Rails::Engine.subclasses.map(&:instance)
+      end
+    end
+  end
+end
+
 module Metasploit
   module Concern
     # Rails engine for Metasploit::Concern that sets up an initializer to load the concerns from app/concerns in other
diff --git a/lib/metasploit/concern/version.rb b/lib/metasploit/concern/version.rb
index bcd9fa8..84140ec 100644
--- a/lib/metasploit/concern/version.rb
+++ b/lib/metasploit/concern/version.rb
@@ -8,6 +8,9 @@ module Version
       MINOR = 0
       # The patch number, scoped to the {MINOR} version number.
       PATCH = 0
+      # the prerelease identifier
+      PRERELEASE = 'rails-4.2'
+
 
       # The full version string, including the {MAJOR}, {MINOR}, {PATCH}, and optionally, the `PRERELEASE` in the
       # {http://semver.org/spec/v2.0.0.html semantic versioning v2.0.0} format.
@@ -16,11 +19,7 @@ module Version
       #   other than master.
       def self.full
         version = "#{MAJOR}.#{MINOR}.#{PATCH}"
-
-        if defined? PRERELEASE
-          version = "#{version}-#{PRERELEASE}"
-        end
-
+        version = "#{version}-#{PRERELEASE}" if defined? PRERELEASE
         version
       end
 
diff --git a/metasploit-concern.gemspec b/metasploit-concern.gemspec
index 3be8755..3d863f4 100644
--- a/metasploit-concern.gemspec
+++ b/metasploit-concern.gemspec
@@ -17,9 +17,8 @@ Gem::Specification.new do |s|
                   'descendents from other gems when layering schemas.'
 
   s.files = Dir['{app,config,lib}/**/*'] + ['CONTRIBUTING.md', 'LICENSE', 'Rakefile', 'README.md'] + Dir['spec/support/**/*.rb']
-  
-  rails_version_constraints = ['>= 4.0.9', '< 4.1.0']
-  
+
+  rails_version_constraints = '>= 4.2.1'
 
   s.required_ruby_version = '>= 2.1'
 
@@ -27,8 +26,8 @@ Gem::Specification.new do |s|
 
   # uses ActiveSupport.on_load to include concerns
   # it is only defined in version 3.0.0 and newer
-  s.add_runtime_dependency 'activerecord', *rails_version_constraints
-  s.add_runtime_dependency 'activesupport', *rails_version_constraints
+  s.add_runtime_dependency 'activerecord', rails_version_constraints
+  s.add_runtime_dependency 'activesupport', rails_version_constraints
   # for engine
-  s.add_runtime_dependency 'railties', *rails_version_constraints
+  s.add_runtime_dependency 'railties', rails_version_constraints
 end
diff --git a/spec/app/models/metasploit/concern/loader_spec.rb b/spec/app/models/metasploit/concern/loader_spec.rb
index bfad298..38b82e4 100644
--- a/spec/app/models/metasploit/concern/loader_spec.rb
+++ b/spec/app/models/metasploit/concern/loader_spec.rb
@@ -73,9 +73,7 @@ def remove_load_hooks
   end
 
   subject(:loader) do
-    described_class.new(
-        root: root
-    )
+    described_class.new(root: root)
   end
 
   #
@@ -83,9 +81,8 @@ def remove_load_hooks
   #
 
   def remove_root
-    if root.exist?
-      root.rmtree
-    end
+    return unless root.exist?
+    root.rmtree
   end
 
   def root
@@ -225,9 +222,9 @@ def each_pathname_constant(&block)
     it 'yields concerns' do
       concern_names = []
 
-      each_pathname_constant { |constant|
+      each_pathname_constant do |constant|
         concern_names << constant.name
-      }
+      end
 
       expect(concern_names).to match_array([concern_name])
     end
@@ -251,9 +248,9 @@ def each_pathname_constant(&block)
     end
 
     let(:expected_module_pathnames) do
-      Array.new(2) { |i|
+      Array.new(2) do |i|
         root.join('metasploit', 'concern', "module_with_concerns#{i}")
-      }
+      end
     end
 
     let(:non_module_pathname) do
@@ -267,9 +264,9 @@ def each_pathname_constant(&block)
         expected_module_pathname.mkpath
         concern_pathname = expected_module_pathname.join('concern_for_module.rb')
 
-        concern_pathname.open('w') { |f|
+        concern_pathname.open('w') do |f|
           f.puts '# A concern'
-        }
+        end
       end
     end
 
@@ -353,19 +350,17 @@ def each_pathname_constant(&block)
         end
 
         it 'has base class loaded' do
-          expect {
+          expect do
             Metasploit::Concern::ModuleWithConcerns
-          }.not_to raise_error
+          end.not_to raise_error
 
           expect(Metasploit::Concern::ModuleWithConcerns).to be_a Class
         end
 
         it 'includes concerns' do
-          expect {
-            register
-          }.to change {
-                 Metasploit::Concern::ModuleWithConcerns.ancestors.map(&:name).include? concern_name
-               }.to(true)
+          expect { register }.to change {
+            Metasploit::Concern::ModuleWithConcerns.ancestors.map(&:name).include? concern_name
+          }.to(true)
         end
 
         it 'does not end up with two copies of concern when reloaded' do
@@ -374,15 +369,13 @@ def each_pathname_constant(&block)
           Metasploit::Concern::ModuleWithConcerns
           expect(Metasploit::Concern::ModuleWithConcerns.ancestors.map(&:name).count(concern_name)).to eq(1)
 
-          expect {
-            ActiveSupport::Dependencies.clear
-          }.not_to change {
-                 Metasploit::Concern::ModuleWithConcerns.constants.include? concern_relative_name.to_sym
-               }
+          expect { ActiveSupport::Dependencies.clear }.not_to change {
+            Metasploit::Concern::ModuleWithConcerns.constants.include? concern_relative_name.to_sym
+          }
 
           Metasploit::Concern::ModuleWithConcerns.send(
-              :include,
-              Metasploit::Concern::ModuleWithConcerns::ConcernForModule
+            :include,
+            Metasploit::Concern::ModuleWithConcerns::ConcernForModule
           )
 
           expect(Metasploit::Concern::ModuleWithConcerns.ancestors.map(&:name).count(concern_name)).to eq(1)
@@ -395,19 +388,17 @@ def each_pathname_constant(&block)
         end
 
         it 'has base class loaded' do
-          expect {
+          expect do
             Metasploit::Concern::ModuleWithConcerns
-          }.not_to raise_error
+          end.not_to raise_error
 
           expect(Metasploit::Concern::ModuleWithConcerns).to be_a Class
         end
 
         it 'includes concerns' do
-          expect {
-            register
-          }.to change {
-                 Metasploit::Concern::ModuleWithConcerns.ancestors.map(&:name).include? concern_name
-               }.to(true)
+          expect { register }.to change {
+            Metasploit::Concern::ModuleWithConcerns.ancestors.map(&:name).include? concern_name
+          }.to(true)
         end
 
         it 'does not end up with two copies of concern when reloaded and included' do
@@ -470,4 +461,4 @@ def each_pathname_constant(&block)
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/dummy/app/concerns/dummy/model_with_concern/concern_for_model.rb b/spec/dummy/app/concerns/dummy/model_with_concern/concern_for_model.rb
index be54ad9..19d3e45 100644
--- a/spec/dummy/app/concerns/dummy/model_with_concern/concern_for_model.rb
+++ b/spec/dummy/app/concerns/dummy/model_with_concern/concern_for_model.rb
@@ -7,11 +7,9 @@ module Dummy::ModelWithConcern::ConcernForModel
 
   module ClassMethods
     def class_method_from_concern
-
     end
   end
 
   def instance_method_from_concern
-
   end
-end
\ No newline at end of file
+end
diff --git a/spec/dummy/app/helpers/.gitkeep b/spec/dummy/app/helpers/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/spec/dummy/app/helpers/application_helper.rb b/spec/dummy/app/helpers/application_helper.rb
deleted file mode 100644
index de6be79..0000000
--- a/spec/dummy/app/helpers/application_helper.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-module ApplicationHelper
-end
diff --git a/spec/dummy/app/models/dummy/model_with_concern.rb b/spec/dummy/app/models/dummy/model_with_concern.rb
index ba42a97..07adc8b 100644
--- a/spec/dummy/app/models/dummy/model_with_concern.rb
+++ b/spec/dummy/app/models/dummy/model_with_concern.rb
@@ -1,3 +1,3 @@
 class Dummy::ModelWithConcern
   ActiveSupport.run_load_hooks(:dummy_model_with_concern, self)
-end
\ No newline at end of file
+end
diff --git a/spec/dummy/config/application.rb b/spec/dummy/config/application.rb
index 842b9d1..c6788ef 100644
--- a/spec/dummy/config/application.rb
+++ b/spec/dummy/config/application.rb
@@ -49,4 +49,3 @@ class Application < Rails::Application
     config.paths.add 'app/concerns', autoload: true
   end
 end
-
diff --git a/spec/dummy/config/boot.rb b/spec/dummy/config/boot.rb
index eba0681..5be62d5 100644
--- a/spec/dummy/config/boot.rb
+++ b/spec/dummy/config/boot.rb
@@ -7,4 +7,4 @@
   Bundler.setup
 end
 
-$:.unshift File.expand_path('../../../../lib', __FILE__)
\ No newline at end of file
+$:.unshift File.expand_path('../../../../lib', __FILE__)
diff --git a/spec/lib/metasploit/concern/engine_spec.rb b/spec/lib/metasploit/concern/engine_spec.rb
index af71708..5aa9d78 100644
--- a/spec/lib/metasploit/concern/engine_spec.rb
+++ b/spec/lib/metasploit/concern/engine_spec.rb
@@ -17,9 +17,9 @@
         # lets
         #
 
-        let(:application) {
+        let(:application) do
           Class.new(Rails::Engine)
-        }
+        end
 
         let(:context) {
           Object.new
@@ -177,4 +177,4 @@
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/lib/metasploit/concern_spec.rb b/spec/lib/metasploit/concern_spec.rb
index 4d6de82..bf10a69 100644
--- a/spec/lib/metasploit/concern_spec.rb
+++ b/spec/lib/metasploit/concern_spec.rb
@@ -12,4 +12,4 @@
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index edc38dd..e1e5be0 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,6 +1,7 @@
 # This file is copied to spec/ when you run 'rails generate rspec:install'
 ENV["RAILS_ENV"] ||= 'test'
 
+require 'minitest/autorun'
 require 'rubygems'
 require 'bundler'
 Bundler.setup(:default, :test)
@@ -15,8 +16,8 @@
   SimpleCov.formatter = Coveralls::SimpleCov::Formatter
 else
   SimpleCov.formatter = SimpleCov::Formatter::MultiFormatter[
-      # either generate the local report
-      SimpleCov::Formatter::HTMLFormatter
+    # either generate the local report
+    SimpleCov::Formatter::HTMLFormatter
   ]
 end
 
diff --git a/spec/support/shared/examples/metasploit/concern/run.rb b/spec/support/shared/examples/metasploit/concern/run.rb
index 64d2518..7f430b9 100644
--- a/spec/support/shared/examples/metasploit/concern/run.rb
+++ b/spec/support/shared/examples/metasploit/concern/run.rb
@@ -31,4 +31,4 @@
       expect(actual_bases).to include(described_class)
     end
   end
-end
\ No newline at end of file
+end