diff --git a/.gitignore b/.gitignore
index b6db9ec..604e863 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@ gemfiles/*.lock
 gemfiles/.bundle/
 tmp/
 .rubocop-*
+/coverage/
diff --git a/.pryrc b/.pryrc
new file mode 100644
index 0000000..68b1922
--- /dev/null
+++ b/.pryrc
@@ -0,0 +1,7 @@
+# Alieases for debugger.
+if defined?(PryByebug) || defined?(PryDebugger)
+  Pry.commands.alias_command 'c', 'continue'
+  Pry.commands.alias_command 's', 'step'
+  Pry.commands.alias_command 'n', 'next'
+  Pry.commands.alias_command 'f', 'finish'
+end
diff --git a/Gemfile b/Gemfile
index 7700f4f..73e4987 100644
--- a/Gemfile
+++ b/Gemfile
@@ -15,6 +15,7 @@ gem 'rails'
 gem 'sidekiq'
 
 gem 'test-unit'
+gem 'simplecov', require: false
 gem 'mocha'
 gem 'thoughtbot-shoulda', '>= 2.9.0'
 
diff --git a/Rakefile b/Rakefile
index 3582859..12a4fe0 100644
--- a/Rakefile
+++ b/Rakefile
@@ -3,7 +3,6 @@ require 'rake/testtask'
 require 'rdoc/task'
 
 $LOAD_PATH << File.join(File.dirname(__FILE__), 'lib')
-require 'paperclip'
 
 import 'lib/tasks/paperclip_tasks.rake'
 
@@ -19,7 +18,7 @@ Rake::TestTask.new(:test) do |t|
 end
 
 desc 'Start an IRB session with all necessary files required.'
-task :shell do
+task :shell => :load_paperclip do
   chdir File.dirname(__FILE__)
   exec 'irb -I lib/ -I lib/paperclip -r rubygems -r active_record -r tempfile -r init'
 end
@@ -62,23 +61,28 @@ exclude_file_globs = ["test/s3.yml",
                       "test/pkg/*",
                       "test/tmp",
                       "test/tmp/*"]
-spec = Gem::Specification.new do |s|
-  s.name              = "paperclip"
-  s.version           = Paperclip::VERSION
-  s.author            = "Jon Yurek"
-  s.email             = "jyurek@thoughtbot.com"
-  s.homepage          = "http://www.thoughtbot.com/projects/paperclip"
-  s.platform          = Gem::Platform::RUBY
-  s.summary           = "File attachments as attributes for ActiveRecord"
-  s.files             = FileList[include_file_globs].to_a - FileList[exclude_file_globs].to_a
-  s.require_path      = "lib"
-  s.test_files        = FileList["test/**/test_*.rb"].to_a
-  s.rubyforge_project = "paperclip"
-  s.extra_rdoc_files  = FileList["README*"].to_a
-  s.rdoc_options << '--line-numbers' << '--inline-source'
-  s.requirements << "ImageMagick"
-  s.add_development_dependency 'thoughtbot-shoulda'
-  s.add_development_dependency 'mocha'
+
+def spec
+  # TODO: require 'paperclip/version'
+  require 'paperclip'
+  Gem::Specification.new do |s|
+    s.name              = "paperclip"
+    s.version           = Paperclip::VERSION
+    s.author            = "Jon Yurek"
+    s.email             = "jyurek@thoughtbot.com"
+    s.homepage          = "http://www.thoughtbot.com/projects/paperclip"
+    s.platform          = Gem::Platform::RUBY
+    s.summary           = "File attachments as attributes for ActiveRecord"
+    s.files             = FileList[include_file_globs].to_a - FileList[exclude_file_globs].to_a
+    s.require_path      = "lib"
+    s.test_files        = FileList["test/**/test_*.rb"].to_a
+    s.rubyforge_project = "paperclip"
+    s.extra_rdoc_files  = FileList["README*"].to_a
+    s.rdoc_options << '--line-numbers' << '--inline-source'
+    s.requirements << "ImageMagick"
+    s.add_development_dependency 'thoughtbot-shoulda'
+    s.add_development_dependency 'mocha'
+  end
 end
 
 desc "Print a list of the files to be put into the gem"
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 3e4684e..5e8c15b 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 require 'rubygems'
+require 'bundler/setup'
+
 require 'test/unit'
 require 'shoulda'
 require 'mocha/test_unit'
@@ -13,6 +15,24 @@ require 'active_record'
 require 'active_support'
 require 'rails'
 
+if ENV['COVERAGE']
+  require 'simplecov'
+
+  SimpleCov.external_at_exit = true
+  Test::Unit.at_exit do
+    SimpleCov.at_exit_behavior
+  end
+  SimpleCov.command_name 'test:units'
+  SimpleCov.start do
+    load_profile "test_frameworks"
+
+    add_group "Storage", "lib/paperclip/storage/"
+    add_group "Libraries", "lib/"
+
+    track_files "{lib}/**/*.rb"
+  end
+end
+
 ROOT = File.expand_path('../', __dir__)
 
 ENV['RAILS_ENV'] = 'test'
@@ -20,9 +40,10 @@ class TestRailsApp < Rails::Application; end
 Rails.application.config.root = "#{ROOT}/tmp/rails"
 
 $LOAD_PATH << File.join(ROOT, 'lib')
-$LOAD_PATH << File.join(ROOT, 'lib', 'paperclip')
+$LOAD_PATH << File.join(ROOT, 'lib/paperclip') # ??
 
-require File.join(ROOT, 'lib', 'paperclip.rb')
+require 'paperclip'
+# require File.join(ROOT, 'lib/paperclip.rb')
 
 require 'shoulda_macros/paperclip'