diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..005119b
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+2.4.1
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..e9a4586
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+gem "rake", "~> 12.0"
+gem "git-cop", "~> 1.0"
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..5bd055d
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,25 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    git-cop (1.0.0)
+      refinements (~> 4.1)
+      runcom (~> 1.1)
+      thor (~> 0.19)
+      thor_plus (~> 5.1)
+    rake (12.0.0)
+    refinements (4.1.0)
+    runcom (1.1.0)
+      refinements (~> 4.1)
+    thor (0.19.4)
+    thor_plus (5.1.0)
+      thor (~> 0.19)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  git-cop (~> 1.0)
+  rake (~> 12.0)
+
+BUNDLED WITH
+   1.15.1
diff --git a/README.md b/README.md
index 2860ebf..384478b 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
 # macOS
 
+[![Circle CI Status](https://circleci.com/gh/bkuhlmann/mac_os.svg?style=svg)](https://circleci.com/gh/bkuhlmann/mac_os)
 [![Patreon](https://img.shields.io/badge/patreon-donate-brightgreen.svg)](https://www.patreon.com/bkuhlmann)
 
 Shell scripts for automated macOS machine setup.
diff --git a/Rakefile b/Rakefile
new file mode 100644
index 0000000..97d01e1
--- /dev/null
+++ b/Rakefile
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+begin
+  require "git/cop/rake/setup"
+rescue LoadError => error
+  puts error.message
+end
+
+task default: :git_cop
diff --git a/circle.yml b/circle.yml
new file mode 100644
index 0000000..869894f
--- /dev/null
+++ b/circle.yml
@@ -0,0 +1,7 @@
+dependencies:
+  pre:
+    - gem update --system
+    - gem update bundler
+test:
+  override:
+    - bundle exec rake