diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..84e28cd
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,32 @@
+name: CI
+
+on:
+  push:
+    branches: [ master, main ]
+  pull_request:
+    branches: [ master, main ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby-version: ['3.0', '3.1', '3.2', '3.3']
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Ruby ${{ matrix.ruby-version }}
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{ matrix.ruby-version }}
+        bundler-cache: true
+
+    - name: Configure git
+      run: |
+        git config --global user.name "Test User"
+        git config --global user.email "test@example.com"
+        git config --global init.defaultBranch master
+
+    - name: Run tests
+      run: bundle exec rake spec
diff --git a/.gitignore b/.gitignore
index 3d120c8..f659bb0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,6 @@ doc/*
 pkg/*
 test/repo
 html/*
+vendor/
+.bundle/
+Gemfile.lock
diff --git a/Gemfile b/Gemfile
index 886bd8b..ab3ae0a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,2 +1,4 @@
+source 'https://rubygems.org'
+
 gem 'rake'
 gem 'rspec'
diff --git a/git_store.gemspec b/git_store.gemspec
index 2c10386..921df6d 100644
--- a/git_store.gemspec
+++ b/git_store.gemspec
@@ -13,7 +13,6 @@ repository. GitStore checks out the repository into a in-memory
 representation, which can be modified and finally committed.
 END
   s.require_path = 'lib'
-  s.has_rdoc = true
   s.extra_rdoc_files = ['README.md']  
   s.files = %w{
 .gitignore
@@ -34,7 +33,10 @@ test/bare_store_spec.rb
 test/benchmark.rb
 test/commit_spec.rb
 test/git_store_spec.rb
+test/helper.rb
+test/spec_helper.rb
 test/tree_spec.rb
+test/user_spec.rb
 }
 end
 
diff --git a/lib/git_store.rb b/lib/git_store.rb
index d5d91eb..671becc 100644
--- a/lib/git_store.rb
+++ b/lib/git_store.rb
@@ -59,8 +59,8 @@ class GitStore
 
   # Initialize a store.
   def initialize(path, branch = 'master', bare = false)
-    if bare && !File.exists?("#{path}") or
-        !bare && !File.exists?("#{path}/.git")
+    if bare && !File.exist?("#{path}") or
+        !bare && !File.exist?("#{path}/.git")
       raise ArgumentError, "first argument must be a valid Git repository: `#{path}'"
     end
 
@@ -105,7 +105,7 @@ def git_path
   #
   # Returns the object id of the last commit.
   def read_head_id
-    File.read(head_path).strip if File.exists?(head_path)
+    File.read(head_path).strip if File.exist?(head_path)
   end
 
   # Return a handler for a given path.
@@ -321,7 +321,7 @@ def id_for(type, content)
   def get_object(id)
     path = object_path(id)
 
-    if File.exists?(path)
+    if File.exist?(path)
       buf = open(path, "rb") { |f| f.read }
 
       raise "not a loose object: #{id}" if not legacy_loose_object?(buf)
@@ -345,7 +345,7 @@ def put_object(type, content)
     id = sha(data)
     path = object_path(id)
 
-    unless File.exists?(path)
+    unless File.exist?(path)
       FileUtils.mkpath(File.dirname(path))
       open(path, 'wb') do |f|
         f.write Zlib::Deflate.deflate(data)
diff --git a/lib/git_store/commit.rb b/lib/git_store/commit.rb
index 01ebbad..dee367d 100644
--- a/lib/git_store/commit.rb
+++ b/lib/git_store/commit.rb
@@ -40,7 +40,9 @@ def parse(data)
 
     def diff(commit, path = nil)
       commit = commit.id if Commit === commit
-      Diff.exec(store, "git diff --full-index #{commit} #{id} -- '#{path}'")
+      cmd = "git diff --full-index #{commit} #{id}"
+      cmd += " -- '#{path}'" if path
+      Diff.exec(store, cmd)
     end
 
     def diffs(path = nil)
diff --git a/lib/git_store/handlers.rb b/lib/git_store/handlers.rb
index e3167c4..ef7acda 100644
--- a/lib/git_store/handlers.rb
+++ b/lib/git_store/handlers.rb
@@ -1,16 +1,4 @@
-
-# This fix ensures sorted yaml maps.
-class Hash
-	def to_yaml( opts = {} )
-		YAML::quick_emit( object_id, opts ) do |out|
-      out.map( taguri, to_yaml_style ) do |map|
-        sort_by { |k, v| k.to_s }.each do |k, v|
-          map.add( k, v )
-        end
-      end
-    end
-	end
-end
+require 'date'
 
 class GitStore
 
@@ -26,7 +14,7 @@ def write(data)
 
   class YAMLHandler
     def read(data)
-      YAML.load(data)
+      YAML.safe_load(data, permitted_classes: [Symbol, Date, Time])
     end
 
     def write(data)
diff --git a/lib/git_store/pack.rb b/lib/git_store/pack.rb
index fb5c43d..451c547 100644
--- a/lib/git_store/pack.rb
+++ b/lib/git_store/pack.rb
@@ -44,7 +44,7 @@ def [](*idx)
       when Range
         offset = idx.first
         len = idx.last - idx.first + idx.exclude_end? ? 0 : 1
-      when Fixnum
+      when Integer
         offset = idx
         len = nil
       when Array
diff --git a/lib/git_store/user.rb b/lib/git_store/user.rb
index a17fc67..37b6dbc 100644
--- a/lib/git_store/user.rb
+++ b/lib/git_store/user.rb
@@ -19,9 +19,9 @@ def self.config_get(key)
 
       if $?.exitstatus == 0
         return value unless value.empty?
-        raise RuntimError, "#{key} is empty"
+        raise RuntimeError, "#{key} is empty"
       else
-        raise RuntimError, "No #{key} found in git config"
+        raise RuntimeError, "No #{key} found in git config"
       end
     end
 
diff --git a/test/bare_store_spec.rb b/test/bare_store_spec.rb
index c33360e..2be2af3 100644
--- a/test/bare_store_spec.rb
+++ b/test/bare_store_spec.rb
@@ -1,4 +1,5 @@
 require "#{File.dirname(__FILE__)}/../lib/git_store"
+require "#{File.dirname(__FILE__)}/spec_helper"
 require "#{File.dirname(__FILE__)}/helper"
 require 'pp'
 
@@ -14,6 +15,8 @@
     Dir.chdir REPO
 
     `git init --bare`
+    `git config user.name 'User Name'`
+    `git config user.email 'user.name@email.com'`
     @store = GitStore.new(REPO, 'master', true)
   end
 
diff --git a/test/commit_spec.rb b/test/commit_spec.rb
index c3a2211..231a2db 100644
--- a/test/commit_spec.rb
+++ b/test/commit_spec.rb
@@ -1,4 +1,5 @@
 require "#{File.dirname(__FILE__)}/../lib/git_store"
+require "#{File.dirname(__FILE__)}/spec_helper"
 require 'pp'
 
 describe GitStore::Commit do
@@ -12,6 +13,8 @@
     Dir.mkdir REPO
     Dir.chdir REPO
     `git init`
+    `git config user.name 'User Name'`
+    `git config user.email 'user.name@email.com'`
     @store = GitStore.new(REPO)
   end
 
@@ -69,13 +72,13 @@
     diff = b.diff(a)
 
     diff[0].a_path.should == 'x'
-    diff[0].deleted_file.should be_true
+    diff[0].deleted_file.should be true
 
     diff[1].a_path.should == 'y'
     diff[1].diff.should == "--- a/y\n+++ b/y\n@@ -1,4 +1,4 @@\n \n First Line.\n-Second Line.\n Last Line.\n+Another Line."
 
     diff[2].a_path.should == 'z'
-    diff[2].new_file.should be_true
+    diff[2].new_file.should be true
   end
   
 end
diff --git a/test/git_store_spec.rb b/test/git_store_spec.rb
index 3d09940..5ba2563 100644
--- a/test/git_store_spec.rb
+++ b/test/git_store_spec.rb
@@ -1,4 +1,5 @@
 require "#{File.dirname(__FILE__)}/../lib/git_store"
+require "#{File.dirname(__FILE__)}/spec_helper"
 require "#{File.dirname(__FILE__)}/helper"
 require 'pp'
 
diff --git a/test/spec_helper.rb b/test/spec_helper.rb
new file mode 100644
index 0000000..e057e98
--- /dev/null
+++ b/test/spec_helper.rb
@@ -0,0 +1,5 @@
+RSpec.configure do |config|
+  config.expect_with :rspec do |expectations|
+    expectations.syntax = [:should, :expect]
+  end
+end
diff --git a/test/tree_spec.rb b/test/tree_spec.rb
index 9e8c93d..2732d8d 100644
--- a/test/tree_spec.rb
+++ b/test/tree_spec.rb
@@ -1,4 +1,5 @@
 require "#{File.dirname(__FILE__)}/../lib/git_store"
+require "#{File.dirname(__FILE__)}/spec_helper"
 require "#{File.dirname(__FILE__)}/helper"
 require 'pp'
 
diff --git a/test/user_spec.rb b/test/user_spec.rb
index 6c9a43a..2f04042 100644
--- a/test/user_spec.rb
+++ b/test/user_spec.rb
@@ -1,4 +1,5 @@
 require "#{File.dirname(__FILE__)}/../lib/git_store"
+require "#{File.dirname(__FILE__)}/spec_helper"
 require 'pp'
 
 describe GitStore::User do