diff --git a/Dockerfile b/Dockerfile
index 90376d4..fbf53b1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,14 +1,17 @@
-FROM ruby:2.6-alpine
+FROM ruby:2.7.7-alpine3.16
 
-MAINTAINER Ryan Davis
+LABEL maintainer="Ryan Davis"
 
 WORKDIR /usr/src/app
 
-RUN gem install --silent hoe minitest rake && \
-    gem install ruby_parser --version 3.13.1 &&  \
-    gem install --silent flog -N -v "~> 4.6" # currently 4.6.4
+COPY Gemfile /usr/src/app/
+COPY Gemfile.lock /usr/src/app/
 
-RUN adduser -u 9000 -D -h /usr/src/app -s /bin/false app
+RUN apk update && \
+    apk add git && \
+    bundle
+
+RUN adduser -u 9000 -D -g "app" app
 COPY . /usr/src/app
 RUN chown -R app:app /usr/src/app
 
diff --git a/Gemfile b/Gemfile
new file mode 100644
index 0000000..16fed1a
--- /dev/null
+++ b/Gemfile
@@ -0,0 +1,12 @@
+source "https://rubygems.org"
+
+gem "hoe"
+gem "minitest"
+gem "rake"
+gem "ruby_parser", "3.13.1"
+gem "flog", "~> 4.6"
+
+group :test do
+  gem "rspec"
+  gem "simplecov"
+end
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..5b9ad01
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,51 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    diff-lcs (1.5.0)
+    docile (1.4.0)
+    flog (4.6.6)
+      path_expander (~> 1.0)
+      ruby_parser (~> 3.1, > 3.1.0)
+      sexp_processor (~> 4.8)
+    hoe (4.0.1)
+      rake (>= 0.8, < 15.0)
+    minitest (5.16.3)
+    path_expander (1.1.1)
+    rake (13.0.6)
+    rspec (3.12.0)
+      rspec-core (~> 3.12.0)
+      rspec-expectations (~> 3.12.0)
+      rspec-mocks (~> 3.12.0)
+    rspec-core (3.12.0)
+      rspec-support (~> 3.12.0)
+    rspec-expectations (3.12.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.12.0)
+    rspec-mocks (3.12.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.12.0)
+    rspec-support (3.12.0)
+    ruby_parser (3.13.1)
+      sexp_processor (~> 4.9)
+    sexp_processor (4.16.1)
+    simplecov (0.21.2)
+      docile (~> 1.1)
+      simplecov-html (~> 0.11)
+      simplecov_json_formatter (~> 0.1)
+    simplecov-html (0.12.3)
+    simplecov_json_formatter (0.1.4)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  flog (~> 4.6)
+  hoe
+  minitest
+  rake
+  rspec
+  ruby_parser (= 3.13.1)
+  simplecov
+
+BUNDLED WITH
+   2.1.4
diff --git a/lib/cc/engine/flog.rb b/lib/cc/engine/flog.rb
index 10c82a9..7bae3e8 100644
--- a/lib/cc/engine/flog.rb
+++ b/lib/cc/engine/flog.rb
@@ -25,20 +25,17 @@ class Flog
                  }
 
       def initialize(root, config = {}, io = STDOUT)
-        self.dir    = root
-        self.config = config = normalize_conf config
-        self.io     = io
+        @dir = root
+        @config = config = normalize_conf(config)
+        @io = io
 
-        options = {
-                   :all       => true,
-                   :continue  => true,
-                  }
+        options = { all: true, continue: true }
 
-        self.flog   = ::Flog.new options
+        @flog   = ::Flog.new(options)
 
         paths = config["include_paths"].dup
-        expander = PathExpander.new paths, "**/*.{rb,rake}"
-        self.files = expander.process.select { |s| s =~ /\.(?:rb|rake)$/ }
+        expander = PathExpander.new(paths, "**/*.{rb,rake}")
+        @files = expander.process.select { |s| s =~ /\.(?:rb|rake)$/ }
       end
 
       ##
@@ -49,13 +46,13 @@ def initialize(root, config = {}, io = STDOUT)
       # https://github.com/codeclimate/codeclimate-yaml/issues/38
       # https://github.com/codeclimate/codeclimate-yaml/issues/39
 
-      def normalize_conf top_config
+      def normalize_conf(top_config)
         # fix the top, if necessary
-        top_config = reparse top_config
+        top_config = reparse(top_config)
         top_config["config"] ||= {}
 
         # normalize contents
-        config = DEFAULTS.merge top_config["config"]
+        config = DEFAULTS.merge(top_config["config"])
         config["include_paths"] = top_config["include_paths"] if
           top_config["include_paths"]
 
@@ -68,13 +65,13 @@ def normalize_conf top_config
       # "false" break a lot of logic. This method reparses the values,
       # recursively if necessary.
 
-      def reparse val
+      def reparse(val)
         require "yaml"
         case val
         when String then
-          YAML.load val
+          YAML.safe_load(val)
         when Array then
-          val.map { |v| reparse v }
+          val.map { |v| reparse(v) }
         when Hash then
           Hash[val.map { |k, v| [reparse(k), reparse(v)] }]
         else
@@ -86,7 +83,7 @@ def reparse val
       # Run flog and print issues as they come up.
 
       def run
-        Dir.chdir dir do
+        Dir.chdir(dir) do
           flog.flog(*files)
 
           flog.each_by_score do |name, score, call_list|
@@ -96,7 +93,7 @@ def run
             next unless score > config["score_threshold"]
 
             datum = "Complex method %s (%.1f)" % [name, score]
-            issue = self.issue name, datum, location, score
+            issue = issue(name, datum, location, score)
 
             if issue then
               io.print issue.to_json
@@ -119,7 +116,7 @@ def run
       ##
       # Create an issue hash from +name+, +datum+, +location+, and +score+.
 
-      def issue name, datum, location, score
+      def issue(name, datum, location, score)
         file, l_start, l_end = [$1, $2.to_i, $3.to_i] if
           location =~ /^(.+?):(\d+)-(\d+)$/