diff --git a/.gitignore b/.gitignore
index fcf9e7b..d0d3c0e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 *~
+coverage
 pkg
 tmp
 Gemfile.lock
diff --git a/process_shared.gemspec b/process_shared.gemspec
index d59b3ee..ebe4c7e 100644
--- a/process_shared.gemspec
+++ b/process_shared.gemspec
@@ -17,4 +17,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency('rake-compiler')
   s.add_development_dependency('minitest')
   s.add_development_dependency('minitest-matchers')
+  s.add_development_dependency('simplecov')
 end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 98ea4ef..926fe4f 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -3,8 +3,12 @@ gem 'minitest'
 require 'minitest/spec'
 require 'minitest/autorun'
 require 'minitest/matchers'
+require 'simplecov'
 
 require 'process_shared'
+SimpleCov.start do
+  add_filter "/spec/"
+end
 
 class RangeMatcher
   def initialize(operator, limit)