diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..d62c32c
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,11 @@
+require: rubocop-rspec
+
+Metrics/LineLength:
+  Max: 100
+
+Style/BlockComments:
+  Exclude:
+    - 'spec/spec_helper.rb'
+
+Layout/EndOfLine:
+  EnforcedStyle: lf # enforce LF line endings on all platforms
diff --git a/Rakefile b/Rakefile
index 51c4f2e..34cd9a8 100644
--- a/Rakefile
+++ b/Rakefile
@@ -6,6 +6,9 @@ Gem::Tasks.new
 require 'rspec/core/rake_task'
 RSpec::Core::RakeTask.new
 
+require 'rubocop/rake_task'
+RuboCop::RakeTask.new
+
 Rake::ExtensionTask.new 'clocale' do |ext|
   ext.lib_dir = 'lib/clocale'
 end
@@ -17,4 +20,4 @@ task test: %w[compile] do
 end
 
 task spec: :compile
-task default: :spec
+task default: %i[spec rubocop]
diff --git a/clocale.gemspec b/clocale.gemspec
index 852b0a3..2c51581 100644
--- a/clocale.gemspec
+++ b/clocale.gemspec
@@ -3,19 +3,21 @@ Gem::Specification.new do |spec|
   spec.version       = '0.0.3'
   spec.authors       = ['Claudio Bley']
   spec.email         = ['claudio.bley@gmail.com']
-  spec.summary       = "A Ruby gem that wraps C locale functions."
+  spec.summary       = 'A Ruby gem that wraps C locale functions.'
   spec.homepage      = 'https://github.com/avdv/clocale'
   spec.license       = 'MIT'
 
   spec.extensions = %w[ext/clocale/extconf.rb]
 
   spec.files = `git ls-files -z`.split("\x0").reject do |f|
-    f.match(%r{^.gitignore})
+    f.match(/^.gitignore/)
   end
 
   spec.add_development_dependency 'codecov', '~> 0.1.10'
   spec.add_development_dependency 'rake', '~> 12.3'
   spec.add_development_dependency 'rake-compiler', '~> 1.0'
   spec.add_development_dependency 'rspec', '~> 3.7'
+  spec.add_development_dependency 'rubocop', '~> 0.58'
+  spec.add_development_dependency 'rubocop-rspec', '~> 1.27'
   spec.add_development_dependency 'rubygems-tasks', '~> 0.2'
 end
diff --git a/ext/clocale/extconf.rb b/ext/clocale/extconf.rb
index ab859ef..a7faf26 100644
--- a/ext/clocale/extconf.rb
+++ b/ext/clocale/extconf.rb
@@ -2,7 +2,7 @@
 
 def check_functions
   %w[setlocale strcoll strxfrm].each do |func|
-    abort "missing function `#{ func }``" unless have_func func
+    abort "missing function `#{func}``" unless have_func func
   end
 end
 
diff --git a/lib/clocale.rb b/lib/clocale.rb
index 91a14a1..46ff4fc 100644
--- a/lib/clocale.rb
+++ b/lib/clocale.rb
@@ -1,2 +1 @@
-
 require 'clocale/clocale'
diff --git a/spec/c_locale_spec.rb b/spec/c_locale_spec.rb
new file mode 100644
index 0000000..6573c66
--- /dev/null
+++ b/spec/c_locale_spec.rb
@@ -0,0 +1,17 @@
+require 'clocale'
+
+RSpec.describe CLocale do
+  %i[LC_ALL LC_COLLATE LC_CTYPE LC_MONETARY LC_NUMERIC LC_TIME].each do |const|
+    it "has #{const} constant" do
+      is_expected.to(satisfy { |m| m.const_defined? const })
+    end
+  end
+
+  it 'can call setlocale' do
+    expect { described_class.setlocale(CLocale::LC_ALL, '') }.not_to raise_error
+  end
+
+  it 'raises an error with invalid locales' do
+    expect { described_class.setlocale(CLocale::LC_COLLATE, 'FOOBAR') }.to raise_error(RuntimeError)
+  end
+end
diff --git a/spec/clocale_spec.rb b/spec/clocale_spec.rb
deleted file mode 100644
index f140efd..0000000
--- a/spec/clocale_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require 'clocale'
-
-RSpec.describe CLocale do
-  context 'module' do
-    %i(LC_ALL LC_COLLATE LC_CTYPE LC_MONETARY LC_NUMERIC LC_TIME).each do |const|
-      it "has #{const} constant" do
-        expect(subject).to be_const_defined const
-      end
-    end
-
-    it 'setlocale' do
-      expect { subject.setlocale(CLocale::LC_ALL, '') }.not_to raise_error
-    end
-  end
-end