diff --git a/features/step_definitions/factory_steps.rb b/features/step_definitions/factory_steps.rb
index 6484068f820..8e29104989f 100644
--- a/features/step_definitions/factory_steps.rb
+++ b/features/step_definitions/factory_steps.rb
@@ -10,9 +10,9 @@ def create_user(name, type = 'User')
   category  = Category.where(name: category_name).first_or_create if category_name
   title   ||= "Hello World %i"
   count.times do |i|
-    if defined?(ActiveRecord)
+    if defined?(::ActiveRecord)
       Post.create! title: title % i, body: body, author: author, published_at: published, custom_category_id: category.try(:id)
-    elsif defined?(Mongoid)
+    elsif defined?(::Mongoid)
       Post.create! title: title % i, body: body, author: author, published_at: published, category_id: category.try(:id)
     end
   end
diff --git a/features/support/env.rb b/features/support/env.rb
index ad47de5c5a0..e81d368fdf7 100644
--- a/features/support/env.rb
+++ b/features/support/env.rb
@@ -8,11 +8,19 @@
 
 require File.expand_path('../../../spec/spec_helper', __FILE__)
 
-ENV['RAILS_ROOT'] = File.expand_path("../../../spec/rails/rails-#{ENV["RAILS"]}", __FILE__)
+require 'rails'
+require 'active_record' unless ENV['MONGOID']
+require 'mongoid' if ENV['MONGOID']
+
+orm_name = defined?(::ActiveRecord) ? 'activerecord' : 'mongoid'
+orm_version = defined?(::ActiveRecord) ? ::ActiveRecord.version : ::Mongoid::VERSION
+ENV['RAILS_ROOT'] = File.expand_path("../../../spec/rails/rails-#{Rails::VERSION::STRING}-#{orm_name}-#{orm_version}", __FILE__)
 
 # Create the test app if it doesn't exists
 unless File.exists?(ENV['RAILS_ROOT'])
-  system 'rake setup'
+  require 'rake'
+  load File.expand_path( "../../tasks/test.rake", __FILE__)
+  Rake::Task["setup"].invoke
 end
 
 require 'rails'
@@ -85,7 +93,7 @@
 Cucumber::Rails::World.use_transactional_fixtures = false unless ENV['MONGOID']
 # How to clean your database when transactions are turned off. See
 # http://github.com/bmabey/database_cleaner for more info.
-if defined?(ActiveRecord::Base)
+if defined?(::ActiveRecord::Base)
   begin
     require 'database_cleaner'
     require 'database_cleaner/cucumber'
@@ -94,8 +102,8 @@
   end
 end
 
-if defined?(Mongoid)
-  Mongoid.default_session.drop
+if defined?(::Mongoid)
+  ::Mongoid.default_session.drop
 end
 
 # Warden helpers to speed up login
diff --git a/lib/active_admin.rb b/lib/active_admin.rb
index 6ee8243e30c..92a5019ab55 100644
--- a/lib/active_admin.rb
+++ b/lib/active_admin.rb
@@ -128,5 +128,5 @@ def after_load(&block)
 require 'active_admin/filters'
 
 # Require ORM-specific plugins
-require 'active_admin/object_mapper/active_record' if defined? ActiveRecord
-require 'active_admin/object_mapper/mongoid'       if defined? Mongoid
+require 'active_admin/object_mapper/active_record' if defined? ::ActiveRecord
+require 'active_admin/object_mapper/mongoid'       if defined? ::Mongoid
diff --git a/spec/unit/belongs_to_spec.rb b/spec/unit/belongs_to_spec.rb
index 0366b6ed3c1..c6d903bf17c 100644
--- a/spec/unit/belongs_to_spec.rb
+++ b/spec/unit/belongs_to_spec.rb
@@ -42,11 +42,11 @@
       allow(controller).to receive(:request){ request }
     end
     it 'should be able to access the collection' do
-      if defined?(ActiveRecord)
-        expect(controller.send :collection).to be_a ActiveRecord::Relation
+      if defined?(::ActiveRecord)
+        expect(controller.send :collection).to be_a ::ActiveRecord::Relation
       end
-      if defined?(Mongoid)
-        expect(controller.send :collection).to be_a Mongoid::Criteria
+      if defined?(::Mongoid)
+        expect(controller.send :collection).to be_a ::Mongoid::Criteria
       end
     end
     it 'should be able to build a new resource' do
diff --git a/spec/unit/comments_spec.rb b/spec/unit/comments_spec.rb
index d9ce01c7d80..d20d067bc96 100644
--- a/spec/unit/comments_spec.rb
+++ b/spec/unit/comments_spec.rb
@@ -1,5 +1,5 @@
 require 'rails_helper'
-defined?(ActiveRecord) and
+defined?(::ActiveRecord) and
 describe "Comments" do
   let(:application) { ActiveAdmin::Application.new }
 
diff --git a/spec/unit/filters/filter_form_builder_spec.rb b/spec/unit/filters/filter_form_builder_spec.rb
index 2497d2504b6..380140d5ce8 100644
--- a/spec/unit/filters/filter_form_builder_spec.rb
+++ b/spec/unit/filters/filter_form_builder_spec.rb
@@ -27,7 +27,7 @@ def view.a_helper_method
     view
   end
 
-  let(:i18n_namespace) { defined?(ActiveRecord) ? :activerecord : :mongoid }
+  let(:i18n_namespace) { defined?(::ActiveRecord) ? :activerecord : :mongoid }
 
   def render_filter(search, filters)
     render_arbre_component({filter_args: [search, filters]}, helpers) do
@@ -143,7 +143,7 @@ def filter(name, options = {})
         body
       end
 
-      if defined?(ActiveRecord)
+      if defined?(::ActiveRecord)
         it "should remove original ordering to prevent PostgreSQL error" do
           expect(scope.object.klass).to receive(:reorder).with('title asc') {
             m = double uniq: double(pluck: ['A Title'])
@@ -239,14 +239,14 @@ def filter(name, options = {})
     context "when given as the _id attribute name" do
       let(:body) { Capybara.string(filter :author_id) }
 
-      if defined?(ActiveRecord)
+      if defined?(::ActiveRecord)
         it "should generate a numeric filter" do
           expect(body).to have_selector("label", text: "Author") # really this should be Author ID :/)
           expect(body).to have_selector("option[value=author_id_less_than]")
           expect(body).to have_selector("input#q_author_id[name='q[author_id_equals]']")
         end
       end
-      if defined?(Mongoid)
+      if defined?(::Mongoid)
         it "should generate a select filter" do
           expect(body).to have_selector("label", text: "Author")
           expect(body).to have_selector("select#q_author_id[name='q[author_id_eq]']")
@@ -297,11 +297,11 @@ def filter(name, options = {})
     context "when polymorphic relationship" do
       let(:scope) { ActiveAdmin::Comment.search }
       it "should raise an error if a collection isn't provided" do
-        if defined?(ActiveRecord)
+        if defined?(::ActiveRecord)
           expect { filter :resource }.to raise_error \
             Formtastic::PolymorphicInputWithoutCollectionError
         end
-        if defined?(Mongoid)
+        if defined?(::Mongoid)
           skip "not added yet"
         end
       end
@@ -311,11 +311,11 @@ def filter(name, options = {})
       let(:scope) { Post.search }
       let(:body)  { Capybara.string(filter :category) }
       it "should ignore that foreign key and let Ransack handle it" do
-        if defined?(ActiveRecord)
+        if defined?(::ActiveRecord)
           expect(Post.reflect_on_association(:category).foreign_key).to eq :custom_category_id
           expect(body).to have_selector("select[name='q[category_id_eq]']")
         end
-        defined?(Mongoid) and skip "not added yet"
+        defined?(::Mongoid) and skip "not added yet"
       end
     end
   end # belongs to
@@ -352,23 +352,23 @@ def view.a_helper_method
       let(:body) { Capybara.string(filter :authors) }
 
       it "should generate a select" do
-        defined?(ActiveRecord) and
+        defined?(::ActiveRecord) and
           expect(body).to have_selector("select[name='q[posts_author_id_eq]']")
-        defined?(Mongoid) and skip "not added yet"
+        defined?(::Mongoid) and skip "not added yet"
       end
 
       it "should set the default text to 'Any'" do
-        defined?(ActiveRecord) and
+        defined?(::ActiveRecord) and
           expect(body).to have_selector("option[value='']", text: "Any")
-        defined?(Mongoid) and skip "not added yet"
+        defined?(::Mongoid) and skip "not added yet"
       end
 
       it "should create an option for each related object" do
-        if defined?(ActiveRecord)
+        if defined?(::ActiveRecord)
           expect(body).to have_selector("option[value='#{john.id}']", text: "John Doe")
           expect(body).to have_selector("option[value='#{jane.id}']", text: "Jane Doe")
         end
-        defined?(Mongoid) and skip "not added yet"
+        defined?(::Mongoid) and skip "not added yet"
       end
     end
 
@@ -376,11 +376,11 @@ def view.a_helper_method
       let(:body) { Capybara.string(filter :authors, as: :check_boxes) }
 
       it "should create a check box for each related object" do
-        if defined?(ActiveRecord)
+        if defined?(::ActiveRecord)
           expect(body).to have_selector("input[name='q[posts_author_id_in][]'][type=checkbox][value='#{john.id}']")
           expect(body).to have_selector("input[name='q[posts_author_id_in][]'][type=checkbox][value='#{jane.id}']")
         end
-        defined?(Mongoid) and skip "not added yet"
+        defined?(::Mongoid) and skip "not added yet"
       end
     end
   end
diff --git a/spec/unit/filters/resource_spec.rb b/spec/unit/filters/resource_spec.rb
index 8832ce6659b..b7d7a6c0739 100644
--- a/spec/unit/filters/resource_spec.rb
+++ b/spec/unit/filters/resource_spec.rb
@@ -18,10 +18,10 @@ class Post
   end
 
   it "should return the defaults if no filters are set" do
-    ary = if defined?(ActiveRecord)
+    ary = if defined?(::ActiveRecord)
       [ :author, :body, :category, :created_at, :custom_searcher, :position, :published_at,
         :starred, :taggings, :title, :updated_at ]
-    elsif defined?(Mongoid)
+    elsif defined?(::Mongoid)
       [ :author, :body, :category, :created_at, :custom_searcher, :foo_id, :position,
         :published_at, :starred, :title, :updated_at ]
     end
@@ -107,10 +107,10 @@ class Post
       resource.preserve_default_filters!
       resource.add_filter :count, as: :string
 
-      ary = if defined?(ActiveRecord)
+      ary = if defined?(::ActiveRecord)
         [ :author, :body, :category, :count, :created_at, :custom_searcher, :position,
             :published_at, :starred, :taggings, :title, :updated_at ]
-      elsif defined?(Mongoid)
+      elsif defined?(::Mongoid)
         [ :author, :body, :category, :count, :created_at, :custom_searcher, :foo_id,
           :position, :published_at, :starred, :title, :updated_at ]
       end
diff --git a/spec/unit/form_builder_spec.rb b/spec/unit/form_builder_spec.rb
index 58005414eca..d56f7d12331 100644
--- a/spec/unit/form_builder_spec.rb
+++ b/spec/unit/form_builder_spec.rb
@@ -90,10 +90,10 @@ def build_form(options = {}, form_object = Post.new, &block)
       expect(body).to have_selector("input[type=text][name='post[title]']")
     end
     it "should generate a textarea" do
-      if defined?(ActiveRecord)
+      if defined?(::ActiveRecord)
         expect(body).to have_selector("textarea[name='post[body]']")
       end
-      if defined?(Mongoid)
+      if defined?(::Mongoid)
         expect(body).to have_selector("input[type=text][name='post[body]']")
       end
     end
@@ -224,10 +224,10 @@ def build_form(options = {}, form_object = Post.new, &block)
       expect(body).to have_selector("input[type=text][name='post[title]']")
     end
     it "should have a body textarea" do
-      if defined?(ActiveRecord)
+      if defined?(::ActiveRecord)
         expect(body).to have_selector("textarea[name='post[body]']")
       end
-      if defined?(Mongoid)
+      if defined?(::Mongoid)
         expect(body).to have_selector("input[type=text][name='post[body]']")
       end
     end
@@ -353,16 +353,16 @@ def build_form(options = {}, form_object = Post.new, &block)
         end
         f.inputs do
           f.input :author
-          f.input :published_at if defined?(ActiveRecord)
+          f.input :published_at if defined?(::ActiveRecord)
           # formtastic doesn't generate datetime_select for DateTime field
-          f.input :published_at, as: :datetime_select if defined?(Mongoid)
+          f.input :published_at, as: :datetime_select if defined?(::Mongoid)
         end
       end
     end
     it "should render four inputs" do
       expect(body).to have_selector("input[name='post[title]']", count: 1)
-      expect(body).to have_selector("textarea[name='post[body]']", count: 1) if defined?(ActiveRecord)
-      expect(body).to have_selector("input[type=text][name='post[body]']", count: 1) if defined?(Mongoid)
+      expect(body).to have_selector("textarea[name='post[body]']", count: 1) if defined?(::ActiveRecord)
+      expect(body).to have_selector("input[type=text][name='post[body]']", count: 1) if defined?(::Mongoid)
       expect(body).to have_selector("select[name='post[author_id]']", count: 1)
       expect(body).to have_selector("select[name='post[published_at(1i)]']", count: 1)
       expect(body).to have_selector("select[name='post[published_at(2i)]']", count: 1)
@@ -384,7 +384,7 @@ def build_form(options = {}, form_object = Post.new, &block)
         end
       end
 
-      let(:i18n_namespace) { defined?(ActiveRecord) ? :activerecord : :mongoid }
+      let(:i18n_namespace) { defined?(::ActiveRecord) ? :activerecord : :mongoid }
       let(:valid_html_id) { /^[A-Za-z]+[\w\-\:\.]*$/ }
 
       it "should translate the association name in header" do
@@ -415,8 +415,8 @@ def build_form(options = {}, form_object = Post.new, &block)
 
       it "should render the nested form" do
         expect(body).to have_selector("input[name='category[posts_attributes][0][title]']")
-        expect(body).to have_selector("textarea[name='category[posts_attributes][0][body]']") if defined?(ActiveRecord)
-        expect(body).to have_selector("input[name='category[posts_attributes][0][body]']") if defined?(Mongoid)
+        expect(body).to have_selector("textarea[name='category[posts_attributes][0][body]']") if defined?(::ActiveRecord)
+        expect(body).to have_selector("input[name='category[posts_attributes][0][body]']") if defined?(::Mongoid)
       end
 
       it "should add a link to remove new nested records" do
diff --git a/spec/unit/helpers/collection_spec.rb b/spec/unit/helpers/collection_spec.rb
index 6257d4ce9d1..c0fb999029a 100644
--- a/spec/unit/helpers/collection_spec.rb
+++ b/spec/unit/helpers/collection_spec.rb
@@ -25,19 +25,19 @@
     end
 
     it "should return the collection size for a collection with group by" do
-      if defined?(ActiveRecord)
+      if defined?(::ActiveRecord)
         expect(collection_size(Post.group(:title))).to eq 2
       end
-      if defined?(Mongoid)
+      if defined?(::Mongoid)
         skip "not implemented yet."
       end
     end
 
     it "should return the collection size for a collection with group by, select and custom order" do
-      if defined?(ActiveRecord)
+      if defined?(::ActiveRecord)
         expect(collection_size(Post.select("title, count(*) as nb_posts").group(:title).order("nb_posts"))).to eq 2
       end
-      if defined?(Mongoid)
+      if defined?(::Mongoid)
         skip "not implemented yet."
       end
     end
diff --git a/spec/unit/order_clause_spec.rb b/spec/unit/order_clause_spec.rb
index 05361d78f48..9eec241e084 100644
--- a/spec/unit/order_clause_spec.rb
+++ b/spec/unit/order_clause_spec.rb
@@ -23,10 +23,10 @@
     end
 
     specify '#to_sql prepends table name' do
-      if defined?(ActiveRecord)
+      if defined?(::ActiveRecord)
         expect(subject.to_sql(config)).to eq '"posts"."id" asc'
       end
-      if defined?(Mongoid)
+      if defined?(::Mongoid)
         expect(subject.to_sql(config)).to eq '"id" asc'
       end
     end
diff --git a/spec/unit/resource/naming_spec.rb b/spec/unit/resource/naming_spec.rb
index b706c043881..d171c5ac1c3 100644
--- a/spec/unit/resource/naming_spec.rb
+++ b/spec/unit/resource/naming_spec.rb
@@ -14,8 +14,8 @@ def config(options = {})
       @config ||= Resource.new(namespace, Category, options)
     end
 
-    module ::Mock class Resource < ActiveRecord::Base; end; end if defined?(ActiveRecord)
-    module ::Mock class Resource; include Mongoid::Document; end; end if defined?(Mongoid)
+    module ::Mock class Resource < ::ActiveRecord::Base; end; end if defined?(::ActiveRecord)
+    module ::Mock class Resource; include ::Mongoid::Document; end; end if defined?(::Mongoid)
     module NoActiveModel class Resource; end; end
 
     describe "singular resource name" do
diff --git a/spec/unit/resource_controller/data_access_spec.rb b/spec/unit/resource_controller/data_access_spec.rb
index 0196663dc40..c84daf6fd6c 100644
--- a/spec/unit/resource_controller/data_access_spec.rb
+++ b/spec/unit/resource_controller/data_access_spec.rb
@@ -29,10 +29,10 @@
 
       it "reorders chain" do
         chain = double "ChainObj"
-        if defined?(ActiveRecord)
+        if defined?(::ActiveRecord)
           expect(chain).to receive(:reorder).with('"posts"."id" asc').once.and_return(Post.search)
         end
-        if defined?(Mongoid)
+        if defined?(::Mongoid)
           expect(chain).to receive(:reorder).with('"id" asc').once.and_return(Post.search)
         end
         controller.send :apply_sorting, chain
diff --git a/spec/unit/resource_controller_spec.rb b/spec/unit/resource_controller_spec.rb
index eb4418fae7a..b77d8add7b7 100644
--- a/spec/unit/resource_controller_spec.rb
+++ b/spec/unit/resource_controller_spec.rb
@@ -200,8 +200,8 @@ def call_after_destroy(obj); end
     subject { controller.send :collection }
 
     it {
-      is_expected.to be_a ActiveRecord::Relation if defined?(ActiveRecord)
-      is_expected.to be_a Mongoid::Criteria if defined?(Mongoid)
+      is_expected.to be_a ::ActiveRecord::Relation if defined?(::ActiveRecord)
+      is_expected.to be_a ::Mongoid::Criteria if defined?(::Mongoid)
     }
 
     it "returns a collection of posts" do
diff --git a/spec/unit/resource_spec.rb b/spec/unit/resource_spec.rb
index 4eca5ac90fa..a21966098a9 100644
--- a/spec/unit/resource_spec.rb
+++ b/spec/unit/resource_spec.rb
@@ -232,10 +232,10 @@ def config(options = {})
       let(:resource) { namespace.register(Post) }
       let(:post) { double }
       before do
-        if defined?(ActiveRecord)
+        if defined?(::ActiveRecord)
           allow(Post).to receive(:find_by_id).with('12345') { post }
         end
-        if defined?(Mongoid)
+        if defined?(::Mongoid)
           allow(Post).to receive(:find).with('12345') { post }
         end
       end
@@ -259,10 +259,10 @@ def config(options = {})
         end
 
         it 'can find the post by the custom primary key' do
-          if defined?(ActiveRecord)
+          if defined?(::ActiveRecord)
             expect(resource.find_resource('55555')).to eq different_post
           end
-          if defined?(Mongoid)
+          if defined?(::Mongoid)
             skip "not implemented yet."
           end
         end
@@ -280,10 +280,10 @@ def config(options = {})
         it 'can find the post by controller finder' do
           # If document not found, by default Mongoid's `find_by` raises an error,
           # ActiveRecord's `find_by` always returns nil, but `find_by!` raises an error.
-          if defined?(ActiveRecord)
+          if defined?(::ActiveRecord)
             allow(Post).to receive(:find_by_title!).with('title-name').and_return(post)
           end
-          if defined?(Mongoid)
+          if defined?(::Mongoid)
             allow(Post).to receive(:find_by).with(title: 'title-name').and_return(post)
           end
 
diff --git a/spec/unit/view_helpers/display_name_spec.rb b/spec/unit/view_helpers/display_name_spec.rb
index a0ca425a3e4..7bb98487df2 100644
--- a/spec/unit/view_helpers/display_name_spec.rb
+++ b/spec/unit/view_helpers/display_name_spec.rb
@@ -44,7 +44,7 @@
 
   context "when no display name method is defined" do
     context "on a Rails model" do
-      let(:i18n_namespace) { defined?(ActiveRecord) ? :activerecord : :mongoid }
+      let(:i18n_namespace) { defined?(::ActiveRecord) ? :activerecord : :mongoid }
 
       it "should show the model name" do
         class ThisModel
diff --git a/spec/unit/views/components/attributes_table_spec.rb b/spec/unit/views/components/attributes_table_spec.rb
index 283887cb19e..a7ba9ef2c3f 100644
--- a/spec/unit/views/components/attributes_table_spec.rb
+++ b/spec/unit/views/components/attributes_table_spec.rb
@@ -218,7 +218,7 @@
             end
 
             context "with defined attribute name translation" do
-              let(:i18n_namespace) { defined?(ActiveRecord) ? :activerecord : :mongoid }
+              let(:i18n_namespace) { defined?(::ActiveRecord) ? :activerecord : :mongoid }
 
               it "should have the translated attribute name in the title" do
                 with_translation i18n_namespace => {attributes: {post: {title: 'Translated Title', id: 'Translated Id'}}} do
diff --git a/spec/unit/views/components/paginated_collection_spec.rb b/spec/unit/views/components/paginated_collection_spec.rb
index 5c9fc2dbb40..073ef78d13e 100644
--- a/spec/unit/views/components/paginated_collection_spec.rb
+++ b/spec/unit/views/components/paginated_collection_spec.rb
@@ -165,10 +165,10 @@ def paginated_collection(*args)
       end
 
       it "should display proper message (including number and not hash)" do
-        if defined?(ActiveRecord)
+        if defined?(::ActiveRecord)
           expect(pagination.find_by_class('pagination_information').first.content).to eq "Displaying <b>all 2</b> posts"
         end
-        if defined?(Mongoid)
+        if defined?(::Mongoid)
           skip "not implemented yet."
         end
       end
@@ -181,11 +181,11 @@ def paginated_collection(*args)
       end
 
       it "should display proper message (including number and not hash)" do
-        if defined?(ActiveRecord)
+        if defined?(::ActiveRecord)
           expect(pagination.find_by_class('pagination_information').first.content.gsub('&nbsp;',' ')).
             to eq "Displaying posts <b>1 - 2</b> of <b>3</b> in total"
         end
-        if defined?(Mongoid)
+        if defined?(::Mongoid)
           skip "not implemented yet."
         end
       end
diff --git a/tasks/test.rake b/tasks/test.rake
index 8e9da27f0b3..4f5d4c0baaa 100644
--- a/tasks/test.rake
+++ b/tasks/test.rake
@@ -5,8 +5,8 @@ task :setup, :parallel do |t, args|
     puts "test app #{ENV['RAILS_ROOT']} already exists; skipping"
   else
     system("mkdir spec/rails") unless File.exists?("spec/rails")
-    template_file = defined?(ActiveRecord) ? 'rails_template.rb' : 'rails_template_mongoid.rb'
-    opts = defined?(ActiveRecord) ? nil : '--skip-active-record'
+    template_file = defined?(::ActiveRecord) ? 'rails_template.rb' : 'rails_template_mongoid.rb'
+    opts = defined?(::ActiveRecord) ? nil : '--skip-active-record'
     system "#{'INSTALL_PARALLEL=yes' if args[:parallel]} bundle exec rails new #{ENV['RAILS_ROOT']} -m spec/support/#{template_file} --skip-bundle #{opts}"
     Rake::Task['parallel:after_setup_hook'].invoke if args[:parallel]
   end