diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 66ef1de..35965b9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,6 +7,16 @@ on:
     branches: [main, master]
 
 jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '4.0'
+          bundler-cache: true
+      - run: bundle exec rubocop
+
   test:
     runs-on: ubuntu-latest
     strategy:
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..502968b
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,5 @@
+inherit_gem:
+  rubocop-shopify: rubocop.yml
+
+AllCops:
+  SuggestExtensions: false
diff --git a/Gemfile b/Gemfile
index cb5d9a7..0e2a8f0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,6 +1,12 @@
+# frozen_string_literal: true
+
 source "https://rubygems.org"
 
-git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
+git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
 
 # Specify your gem's dependencies in ast_transform.gemspec
 gemspec
+
+# Transitive dependency of rubocop: parallel >= 2 requires Ruby >= 3.3, but we
+# still support 3.2. Drop this pin when our Ruby floor moves to 3.3.
+gem "parallel", "< 2", require: false
diff --git a/Gemfile.lock b/Gemfile.lock
index e4723d3..d307024 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -16,6 +16,9 @@ GEM
     diff-lcs (1.6.2)
     docile (1.4.1)
     io-console (0.8.2)
+    json (2.21.1)
+    language_server-protocol (3.17.0.6)
+    lint_roller (1.1.0)
     method_source (1.1.0)
     minitest (5.27.0)
     minitest-reporters (1.7.1)
@@ -23,6 +26,7 @@ GEM
       builder
       minitest (>= 5.0)
       ruby-progressbar
+    parallel (1.28.0)
     parser (3.3.10.2)
       ast (~> 2.4.1)
       racc
@@ -32,9 +36,27 @@ GEM
       method_source (~> 1.0)
       reline (>= 0.6.0)
     racc (1.8.1)
+    rainbow (3.1.1)
     rake (13.3.1)
+    regexp_parser (2.12.0)
     reline (0.6.3)
       io-console (~> 0.5)
+    rubocop (1.88.2)
+      json (~> 2.3)
+      language_server-protocol (~> 3.17.0.2)
+      lint_roller (~> 1.1.0)
+      parallel (>= 1.10)
+      parser (>= 3.3.0.2)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 2.9.3, < 3.0)
+      rubocop-ast (>= 1.49.0, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 2.4.0, < 4.0)
+    rubocop-ast (1.50.0)
+      parser (>= 3.3.7.2)
+      prism (~> 1.7)
+    rubocop-shopify (2.18.0)
+      rubocop (~> 1.62)
     ruby-progressbar (1.13.0)
     simplecov (0.22.0)
       docile (~> 1.1)
@@ -42,6 +64,9 @@ GEM
       simplecov_json_formatter (~> 0.1)
     simplecov-html (0.13.2)
     simplecov_json_formatter (0.1.4)
+    unicode-display_width (3.2.0)
+      unicode-emoji (~> 4.1)
+    unicode-emoji (4.2.0)
     unparser (0.8.1)
       diff-lcs (~> 1.6)
       parser (>= 3.3.0)
@@ -56,8 +81,10 @@ DEPENDENCIES
   bundler (>= 2.1)
   minitest (~> 5.14)
   minitest-reporters (~> 1.4)
+  parallel (< 2)
   pry (>= 0.14)
   rake (~> 13.0)
+  rubocop-shopify (~> 2.18)
   simplecov (~> 0.22)
 
 BUNDLED WITH
diff --git a/Rakefile b/Rakefile
index 415d4bf..53c16a0 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,16 +1,17 @@
 # frozen_string_literal: true
-require 'bundler/gem_tasks'
-require 'rake/testtask'
+
+require "bundler/gem_tasks"
+require "rake/testtask"
 
 Rake::TestTask.new(:test) do |t|
   # Ensure we load test_loader first for ASTTransform.install
-  filepath = File.expand_path('test/test_loader.rb', __dir__)
+  filepath = File.expand_path("test/test_loader.rb", __dir__)
   t.ruby_opts << "-r #{filepath}"
   t.warning = false
 
-  t.libs << 'test'
-  t.libs << 'lib'
-  t.test_files = FileList['test/**/*_test.rb']
+  t.libs << "test"
+  t.libs << "lib"
+  t.test_files = FileList["test/**/*_test.rb"]
 end
 
-task :default => :test
+task default: :test
diff --git a/ast_transform.gemspec b/ast_transform.gemspec
index e93e0c3..dd6d03e 100644
--- a/ast_transform.gemspec
+++ b/ast_transform.gemspec
@@ -1,3 +1,4 @@
+# frozen_string_literal: true
 
 lib = File.expand_path("../lib", __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
@@ -9,28 +10,30 @@ Gem::Specification.new do |spec|
   spec.authors       = ["Jean-Philippe Duchesne"]
   spec.email         = ["jpduchesne89@gmail.com"]
 
-  spec.summary       = 'An AST transformation framework.'
+  spec.summary       = "An AST transformation framework."
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/rspockframework/ast-transform"
   spec.license       = "MIT"
-  spec.files         = `git ls-files -z`.split("\x0").reject do |f|
+  spec.files         = %x(git ls-files -z).split("\x0").reject do |f|
     f.match(%r{^(test|spec|features)/})
   end
   spec.bindir        = "exe"
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
-  spec.required_ruby_version = '>= 3.2'
+  spec.required_ruby_version = ">= 3.2"
 
   # Development dependencies
-  spec.add_development_dependency "bundler", ">= 2.1"
-  spec.add_development_dependency "rake", "~> 13.0"
-  spec.add_development_dependency "minitest", "~> 5.14"
-  spec.add_development_dependency "minitest-reporters", "~> 1.4"
-  spec.add_development_dependency "pry", ">= 0.14"
-  spec.add_development_dependency "simplecov", "~> 0.22"
+  spec.add_development_dependency("bundler", ">= 2.1")
+  spec.add_development_dependency("minitest", "~> 5.14")
+  spec.add_development_dependency("minitest-reporters", "~> 1.4")
+  spec.add_development_dependency("pry", ">= 0.14")
+  spec.add_development_dependency("rake", "~> 13.0")
+  # rubocop-shopify >= 3.0 requires Ruby >= 3.3; bump alongside our own floor.
+  spec.add_development_dependency("rubocop-shopify", "~> 2.18")
+  spec.add_development_dependency("simplecov", "~> 0.22")
 
   # Runtime dependencies
-  spec.add_runtime_dependency "parser", ">= 3.0"
-  spec.add_runtime_dependency "prism", ">= 1.5"
-  spec.add_runtime_dependency "unparser", ">= 0.6"
+  spec.add_runtime_dependency("parser", ">= 3.0")
+  spec.add_runtime_dependency("prism", ">= 1.5")
+  spec.add_runtime_dependency("unparser", ">= 0.6")
 end
diff --git a/bin/console b/bin/console
index 7aa6b78..10e617c 100755
--- a/bin/console
+++ b/bin/console
@@ -1,4 +1,5 @@
 #!/usr/bin/env ruby
+# frozen_string_literal: true
 
 require "bundler/setup"
 require "ast_transform"
diff --git a/dev.yml b/dev.yml
new file mode 100644
index 0000000..96a944d
--- /dev/null
+++ b/dev.yml
@@ -0,0 +1,11 @@
+name: ast_transform
+commands:
+  up:
+    desc: Install gems
+    run: bundle install
+  test:
+    desc: Run this repo's tests
+    run: bundle exec rake test
+  style:
+    desc: Run RuboCop
+    run: bundle exec rubocop
diff --git a/lib/ast_transform.rb b/lib/ast_transform.rb
index 9a4e1aa..e07cf69 100644
--- a/lib/ast_transform.rb
+++ b/lib/ast_transform.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 require "ast_transform/version"
-require 'ast_transform/instruction_sequence'
-require 'ast_transform/instruction_sequence/mixin'
-require 'ast_transform/instruction_sequence/bootsnap_mixin'
+require "ast_transform/instruction_sequence"
+require "ast_transform/instruction_sequence/mixin"
+require "ast_transform/instruction_sequence/bootsnap_mixin"
 
 module ASTTransform
   DEFAULT_OUTPUT_PATH = Pathname.new("").join("tmp", "ast_transform").to_s
@@ -19,22 +19,18 @@ def acronym(acronym)
     end
 
     def install
-      @installed ||= begin
-        if defined?(Bootsnap) && ASTTransform::InstructionSequence.using_bootsnap_compilation?
-          class << Bootsnap::CompileCache::ISeq
-            prepend ::ASTTransform::InstructionSequence::BootsnapMixin
-          end
-        else
-          class << RubyVM::InstructionSequence
-            prepend ::ASTTransform::InstructionSequence::Mixin
-          end
+      @installed ||= if defined?(Bootsnap) && ASTTransform::InstructionSequence.using_bootsnap_compilation?
+        class << Bootsnap::CompileCache::ISeq
+          prepend ::ASTTransform::InstructionSequence::BootsnapMixin
+        end
+      else
+        class << RubyVM::InstructionSequence
+          prepend ::ASTTransform::InstructionSequence::Mixin
         end
       end
     end
 
-    def output_path=(path)
-      @output_path = path
-    end
+    attr_writer :output_path
 
     def output_path
       @output_path || DEFAULT_OUTPUT_PATH
diff --git a/lib/ast_transform/abstract_transformation.rb b/lib/ast_transform/abstract_transformation.rb
index f2e06db..782cfe9 100644
--- a/lib/ast_transform/abstract_transformation.rb
+++ b/lib/ast_transform/abstract_transformation.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
-require 'ast_transform/transformation_helper'
+
+require "ast_transform/transformation_helper"
 
 module ASTTransform
   class AbstractTransformation < Parser::AST::Processor
diff --git a/lib/ast_transform/instruction_sequence.rb b/lib/ast_transform/instruction_sequence.rb
index 795d2b3..a4dcdf7 100644
--- a/lib/ast_transform/instruction_sequence.rb
+++ b/lib/ast_transform/instruction_sequence.rb
@@ -1,4 +1,5 @@
 # frozen_string_literal: true
+
 module ASTTransform
   module InstructionSequence
     class << self
@@ -22,12 +23,12 @@ def source_to_transformed_iseq(source, source_path)
       def write_pathname(file_path)
         project_path = File.expand_path("")
         relative_source_file_pathname = Pathname.new(file_path).relative_path_from(Pathname.new(project_path))
-        Pathname.new("").join(project_path, 'tmp', 'ast_transform', relative_source_file_pathname)
+        Pathname.new("").join(project_path, "tmp", "ast_transform", relative_source_file_pathname)
       end
 
       def write(string, pathname)
         FileUtils.mkdir_p(pathname.dirname)
-        File.open(pathname, 'w') do |file|
+        File.open(pathname, "w") do |file|
           file.write(string)
         end
       end
diff --git a/lib/ast_transform/instruction_sequence/bootsnap_mixin.rb b/lib/ast_transform/instruction_sequence/bootsnap_mixin.rb
index 105be30..ece746c 100644
--- a/lib/ast_transform/instruction_sequence/bootsnap_mixin.rb
+++ b/lib/ast_transform/instruction_sequence/bootsnap_mixin.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require 'ast_transform/transformer'
-require 'ast_transform/instruction_sequence/mixin_utils'
-require 'pathname'
+require "ast_transform/transformer"
+require "ast_transform/instruction_sequence/mixin_utils"
+require "pathname"
 
 module ASTTransform
   module InstructionSequence
@@ -14,7 +14,7 @@ def input_to_storage(source, source_path)
         iseq = ASTTransform::InstructionSequence.source_to_transformed_iseq(source, source_path)
         iseq.to_binary
       rescue SyntaxError
-        raise ::Bootsnap::CompileCache::Uncompilable, 'syntax error'
+        raise ::Bootsnap::CompileCache::Uncompilable, "syntax error"
       end
     end
   end
diff --git a/lib/ast_transform/instruction_sequence/mixin.rb b/lib/ast_transform/instruction_sequence/mixin.rb
index a25d839..2d80b4e 100644
--- a/lib/ast_transform/instruction_sequence/mixin.rb
+++ b/lib/ast_transform/instruction_sequence/mixin.rb
@@ -1,8 +1,9 @@
 # frozen_string_literal: true
-require 'pathname'
-require 'ast_transform/transformer'
-require 'ast_transform/transformation'
-require 'ast_transform/instruction_sequence/mixin_utils'
+
+require "pathname"
+require "ast_transform/transformer"
+require "ast_transform/transformation"
+require "ast_transform/instruction_sequence/mixin_utils"
 
 module ASTTransform
   module InstructionSequence
@@ -15,7 +16,7 @@ def load_iseq(source_path)
         # via magic comments, so we never need to set it ourselves.
         source = File.binread(source_path)
 
-        return ASTTransform::MixinUtils.try_super(self, :load_iseq, source_path) unless source.include?('transform!'.b)
+        return ASTTransform::MixinUtils.try_super(self, :load_iseq, source_path) unless source.include?("transform!".b)
 
         ASTTransform::InstructionSequence.source_to_transformed_iseq(source, source_path)
       end
diff --git a/lib/ast_transform/instruction_sequence/mixin_utils.rb b/lib/ast_transform/instruction_sequence/mixin_utils.rb
index eed2694..b37c772 100644
--- a/lib/ast_transform/instruction_sequence/mixin_utils.rb
+++ b/lib/ast_transform/instruction_sequence/mixin_utils.rb
@@ -5,7 +5,7 @@ module MixinUtils
     class << self
       def try_super(target, method_sym, *args, &block)
         super_method = target.method(method_sym).super_method
-        super_method ? super_method.call(*args, &block) : nil
+        super_method&.call(*args, &block)
       end
     end
   end
diff --git a/lib/ast_transform/kwargs_builder.rb b/lib/ast_transform/kwargs_builder.rb
index db5abb5..cc6443a 100644
--- a/lib/ast_transform/kwargs_builder.rb
+++ b/lib/ast_transform/kwargs_builder.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'prism/translation/parser'
+require "prism/translation/parser"
 
 module ASTTransform
   # Extends the default Prism parser builder to distinguish keyword arguments
diff --git a/lib/ast_transform/source_map.rb b/lib/ast_transform/source_map.rb
index 4833ad7..cdc67b8 100644
--- a/lib/ast_transform/source_map.rb
+++ b/lib/ast_transform/source_map.rb
@@ -1,5 +1,6 @@
 # frozen_string_literal: true
-require 'parser'
+
+require "parser"
 
 module ASTTransform
   class SourceMap
@@ -28,7 +29,9 @@ def for_file_path(file_path)
       private
 
       def source_maps
-        @@source_maps ||= {}
+        # Class instance var (not @@): read/written only through this method
+        # inside class << self, and SourceMap has no subclasses to share with.
+        @source_maps ||= {}
       end
     end
 
@@ -97,7 +100,7 @@ def extract_source_map_data(node, indexes)
     #
     # @return [Hash] A Hash containing line numbers from executed code to source code.
     def build_source_map
-      (1..line_count).each.with_object({}) {|it, hash| hash[it] = source_line(it) }
+      (1..line_count).each.with_object({}) { |it, hash| hash[it] = source_line(it) }
     end
 
     # Retrieves the source line for the given +line_number+ in the executed code.
@@ -226,6 +229,7 @@ def dig_last_valid_node(node, indexes)
     def dig_node(node, indexes)
       indexes.inject(node) do |node, index|
         return nil unless node.is_a?(Parser::AST::Node)
+
         node.children[index]
       end
     end
diff --git a/lib/ast_transform/transformation.rb b/lib/ast_transform/transformation.rb
index 17c891f..1fe4caa 100644
--- a/lib/ast_transform/transformation.rb
+++ b/lib/ast_transform/transformation.rb
@@ -1,8 +1,9 @@
 # frozen_string_literal: true
-require 'ast_transform'
-require 'ast_transform/abstract_transformation'
-require 'ast_transform/transformer'
-require 'unparser'
+
+require "ast_transform"
+require "ast_transform/abstract_transformation"
+require "ast_transform/transformer"
+require "unparser"
 
 module ASTTransform
   class Transformation < ASTTransform::AbstractTransformation
@@ -18,9 +19,9 @@ def process_node(node)
 
       count_before_reject = children.size
 
-      children.reject!.with_index { |child_node, index|
+      children.reject!.with_index do |child_node, index|
         transform_node?(child_node) && transformable_node?(next_child(node, index))
-      }
+      end
 
       processed = process_all(children)
 
@@ -68,19 +69,14 @@ def extract_transformations(node)
 
     def extract_transformation(node)
       return unless node.is_a?(Parser::AST::Node)
-      return unless node.children.count >= 2
-
-      if node.children[1] == :new
-        require_transformation(node)
-        code = Unparser.unparse(node)
+      return if node.children.count < 2
 
-        TOPLEVEL_BINDING.eval(code)
-      else
-        require_transformation(node)
-        code = "#{Unparser.unparse(node)}.new"
+      require_transformation(node)
+      code = Unparser.unparse(node)
+      # A bare constant reference is instantiated; an explicit .new is kept as written.
+      code = "#{code}.new" unless node.children[1] == :new
 
-        TOPLEVEL_BINDING.eval(code)
-      end
+      TOPLEVEL_BINDING.eval(code)
     end
 
     def require_transformation(node)
@@ -100,11 +96,12 @@ def require_path(const_name)
       acronyms = ASTTransform.acronyms
       acronym_regex = acronyms.empty? ? /(?=a)b/ : /#{acronyms.join("|")}/
       return const_name unless /[A-Z-]|::/.match?(const_name)
-      word = const_name.to_s.gsub("::".freeze, "/".freeze)
-      word.gsub!(/(?:(?<=([A-Za-z\d]))|\b)(#{acronym_regex})(?=\b|[^a-z])/) { "#{$1 && '_'.freeze }#{$2.downcase}" }
-      word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2'.freeze)
-      word.gsub!(/([a-z\d])([A-Z])/, '\1_\2'.freeze)
-      word.tr!("-".freeze, "_".freeze)
+
+      word = const_name.to_s.gsub("::", "/")
+      word.gsub!(/(?:(?<=([A-Za-z\d]))|\b)(#{acronym_regex})(?=\b|[^a-z])/) { "#{::Regexp.last_match(1) && "_"}#{::Regexp.last_match(2).downcase}" }
+      word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2')
+      word.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
+      word.tr!("-", "_")
       word.downcase!
       word
     end
diff --git a/lib/ast_transform/transformation_helper.rb b/lib/ast_transform/transformation_helper.rb
index 40b2a47..df0f20f 100644
--- a/lib/ast_transform/transformation_helper.rb
+++ b/lib/ast_transform/transformation_helper.rb
@@ -1,11 +1,14 @@
 # frozen_string_literal: true
-require 'parser'
+
+require "parser"
 
 module ASTTransform
   module TransformationHelper
-    def self.included(base)
-      base.extend(Methods)
-      base.include(Methods)
+    class << self
+      def included(base)
+        base.extend(Methods)
+        base.include(Methods)
+      end
     end
 
     module Methods
diff --git a/lib/ast_transform/transformer.rb b/lib/ast_transform/transformer.rb
index 14ea5c7..99508e1 100644
--- a/lib/ast_transform/transformer.rb
+++ b/lib/ast_transform/transformer.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
-require 'prism'
-require 'prism/translation/parser'
-require 'unparser'
-require 'ast_transform/kwargs_builder'
-require 'ast_transform/source_map'
+
+require "prism"
+require "prism/translation/parser"
+require "unparser"
+require "ast_transform/kwargs_builder"
+require "ast_transform/source_map"
 
 module ASTTransform
   class Transformer
@@ -20,7 +21,7 @@ def initialize(*transformations)
     # @param file_path [String] The file_path. This is important for source mapping in backtraces.
     #
     # @return [Parser::AST::Node] The AST.
-    def build_ast(source, file_path: 'tmp')
+    def build_ast(source, file_path: "tmp")
       buffer = create_buffer(source, file_path)
       parser.parse(buffer)
     end
diff --git a/lib/ast_transform/version.rb b/lib/ast_transform/version.rb
index ffb0fcb..b2aa222 100644
--- a/lib/ast_transform/version.rb
+++ b/lib/ast_transform/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module ASTTransform
   VERSION = "2.1.4"
 end
diff --git a/test/ast_transform/abstract_transformation_test.rb b/test/ast_transform/abstract_transformation_test.rb
index fc751cb..b432e80 100644
--- a/test/ast_transform/abstract_transformation_test.rb
+++ b/test/ast_transform/abstract_transformation_test.rb
@@ -1,7 +1,8 @@
 # frozen_string_literal: true
-require 'test_helper'
-require 'transformation_helper'
-require 'ast_transform/abstract_transformation'
+
+require "test_helper"
+require "transformation_helper"
+require "ast_transform/abstract_transformation"
 
 module ASTTransform
   class AbstractTransformationTest < Minitest::Test
diff --git a/test/ast_transform/instruction_sequence/mixin_utils_test.rb b/test/ast_transform/instruction_sequence/mixin_utils_test.rb
index b18e026..4564cfd 100644
--- a/test/ast_transform/instruction_sequence/mixin_utils_test.rb
+++ b/test/ast_transform/instruction_sequence/mixin_utils_test.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
-require 'test_helper'
-require 'ast_transform/instruction_sequence/mixin_utils'
+
+require "test_helper"
+require "ast_transform/instruction_sequence/mixin_utils"
 
 module ASTTransform
   class MixinUtilsTest < Minitest::Test
@@ -8,24 +9,24 @@ class MixinUtilsTest < Minitest::Test
 
     class Base
       def foo
-        'Base#foo'
+        "Base#foo"
       end
     end
 
     class FooBar < Base
       def foo
-        'FooBar#foo'
+        "FooBar#foo"
       end
 
       def bar
-        'FooBar#bar'
+        "FooBar#bar"
       end
     end
 
     test "#try_super when super method is defined" do
       foo_bar = FooBar.new
 
-      assert_equal 'Base#foo', ASTTransform::MixinUtils.try_super(foo_bar, :foo)
+      assert_equal "Base#foo", ASTTransform::MixinUtils.try_super(foo_bar, :foo)
     end
 
     test "#try_super when super method is not defined" do
diff --git a/test/ast_transform/instruction_sequence_test.rb b/test/ast_transform/instruction_sequence_test.rb
index b7a927e..47a92b5 100644
--- a/test/ast_transform/instruction_sequence_test.rb
+++ b/test/ast_transform/instruction_sequence_test.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-require 'test_helper'
-require 'tempfile'
-require 'ast_transform/instruction_sequence'
-require 'ast_transform/instruction_sequence/mixin'
-require 'ast_transform/transformation'
+require "test_helper"
+require "tempfile"
+require "ast_transform/instruction_sequence"
+require "ast_transform/instruction_sequence/mixin"
+require "ast_transform/transformation"
 
 module ASTTransform
   class InstructionSequenceTest < Minitest::Test
@@ -24,12 +24,13 @@ def setup
 
       iseq = ASTTransform::InstructionSequence.source_to_transformed_iseq(source, source_path)
 
-      assert_equal source_path, iseq.path,
+      assert_equal source_path,
+        iseq.path,
         "ISeq should report the original source path, not the tmp/ rewritten path"
     end
 
     test "source_to_transformed_iseq handles binary-encoded source" do
-      source = "# café résumé\n1 + 2\n".dup.force_encoding('ASCII-8BIT')
+      source = "# café résumé\n1 + 2\n".dup.force_encoding("ASCII-8BIT")
       source_path = File.expand_path("test/fixtures/encoding_test.rb")
 
       iseq = ASTTransform::InstructionSequence.source_to_transformed_iseq(source, source_path)
@@ -38,26 +39,26 @@ def setup
     end
 
     test "load_iseq skips non-ASCII files without transform!" do
-      tmpfile = Tempfile.new(['non_ascii', '.rb'])
+      tmpfile = Tempfile.new(["non_ascii", ".rb"])
       tmpfile.write("# café résumé\nx = 1\n")
       tmpfile.close
 
       iseq = @loader.load_iseq(tmpfile.path)
 
-      assert_nil iseq
+      assert_nil(iseq)
     ensure
       tmpfile&.unlink
     end
 
     test "load_iseq processes non-ASCII files with transform! without encoding errors" do
-      tmpfile = Tempfile.new(['non_ascii_transform', '.rb'])
+      tmpfile = Tempfile.new(["non_ascii_transform", ".rb"])
       tmpfile.write("# café résumé\nx = 1\n# transform!\n")
       tmpfile.close
 
       iseq = @loader.load_iseq(tmpfile.path)
 
-      assert_instance_of RubyVM::InstructionSequence, iseq
-      assert_equal tmpfile.path, iseq.path
+      assert_instance_of(RubyVM::InstructionSequence, iseq)
+      assert_equal(tmpfile.path, iseq.path)
     ensure
       tmpfile&.unlink
     end
diff --git a/test/ast_transform/kwargs_builder_test.rb b/test/ast_transform/kwargs_builder_test.rb
index 2adac97..e355613 100644
--- a/test/ast_transform/kwargs_builder_test.rb
+++ b/test/ast_transform/kwargs_builder_test.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require 'test_helper'
-require 'ast_transform/kwargs_builder'
+require "test_helper"
+require "ast_transform/kwargs_builder"
 
 module ASTTransform
   class KwargsBuilderTest < Minitest::Test
@@ -13,7 +13,7 @@ def setup
     end
 
     test "#associate emits :kwargs for bare keyword arguments" do
-      ast = parse('foo(bar: 1, baz: 2)')
+      ast = parse("foo(bar: 1, baz: 2)")
       node = find_node(ast, :kwargs)
 
       refute_nil node, "expected a :kwargs node for bare keyword arguments"
@@ -21,7 +21,7 @@ def setup
     end
 
     test "#associate emits :hash for explicit hash with braces" do
-      ast = parse('foo({ bar: 1, baz: 2 })')
+      ast = parse("foo({ bar: 1, baz: 2 })")
       hash_node = find_node(ast, :hash)
 
       refute_nil hash_node, "expected a :hash node for explicit hash"
@@ -38,7 +38,7 @@ def setup
     end
 
     test "#associate emits :hash for standalone hash literals" do
-      ast = parse('x = { a: 1, b: 2 }')
+      ast = parse("x = { a: 1, b: 2 }")
       hash_node = find_node(ast, :hash)
 
       refute_nil hash_node, "expected a :hash node for hash literal"
@@ -47,7 +47,7 @@ def setup
     end
 
     test "#associate preserves keyword argument pairs" do
-      ast = parse('foo(bar: 1, baz: 2)')
+      ast = parse("foo(bar: 1, baz: 2)")
       node = find_node(ast, :kwargs)
 
       assert_equal 2, node.children.length
@@ -59,7 +59,7 @@ def setup
     end
 
     test "#associate emits :kwargs for keyword arguments in constructor calls" do
-      ast = parse('Foo.new(bar: 1, baz: 2)')
+      ast = parse("Foo.new(bar: 1, baz: 2)")
       node = find_node(ast, :kwargs)
 
       refute_nil node, "expected a :kwargs node in constructor call"
@@ -67,7 +67,7 @@ def setup
     end
 
     test "#associate emits :kwargs for double-splat keyword arguments" do
-      ast = parse('foo(**opts)')
+      ast = parse("foo(**opts)")
       node = find_node(ast, :kwargs)
 
       refute_nil node, "expected a :kwargs node for double-splat"
@@ -76,14 +76,14 @@ def setup
     private
 
     def parse(source)
-      buffer = Parser::Source::Buffer.new('test')
+      buffer = Parser::Source::Buffer.new("test")
       buffer.source = source
       @parser.parse(buffer)
     end
 
     def find_node(ast, type)
       return ast if ast.type == type
-      return nil unless ast.respond_to?(:children)
+      return unless ast.respond_to?(:children)
 
       ast.children.each do |child|
         next unless child.is_a?(Parser::AST::Node)
diff --git a/test/ast_transform/source_map_test.rb b/test/ast_transform/source_map_test.rb
index 2375896..ae7ba57 100644
--- a/test/ast_transform/source_map_test.rb
+++ b/test/ast_transform/source_map_test.rb
@@ -1,8 +1,9 @@
 # frozen_string_literal: true
-require 'test_helper'
-require 'transformation_helper'
-require 'ast_transform/abstract_transformation'
-require 'ast_transform/transformer'
+
+require "test_helper"
+require "transformation_helper"
+require "ast_transform/abstract_transformation"
+require "ast_transform/transformer"
 
 module ASTTransform
   class SourceMapTest < Minitest::Test
@@ -22,11 +23,11 @@ def run(node)
         method_call
       HEREDOC
 
-      actual_transformed_source = transformer.transform_file_source(source, 'src', 'transformed')
+      actual_transformed_source = transformer.transform_file_source(source, "src", "transformed")
 
       assert_equal "method_call + 1", actual_transformed_source
 
-      source_map = ASTTransform::SourceMap.for_file_path('transformed')
+      source_map = ASTTransform::SourceMap.for_file_path("transformed")
 
       assert_equal 1, source_map.line(1)
     end
@@ -44,12 +45,12 @@ def run(node)
         method_call
       HEREDOC
 
-      actual_transformed_source = transformer.transform_file_source(source, 'src', 'transformed')
+      actual_transformed_source = transformer.transform_file_source(source, "src", "transformed")
 
       assert_equal "method_call + 1", actual_transformed_source
 
-      transformer.transform_file_source(source, 'src', 'transformed')
-      source_map = ASTTransform::SourceMap.for_file_path('transformed')
+      transformer.transform_file_source(source, "src", "transformed")
+      source_map = ASTTransform::SourceMap.for_file_path("transformed")
 
       assert_equal 1, source_map.line(1)
     end
@@ -68,11 +69,11 @@ def run(node)
         method_call2
       HEREDOC
 
-      actual_transformed_source = transformer.transform_file_source(source, 'src', 'transformed')
+      actual_transformed_source = transformer.transform_file_source(source, "src", "transformed")
 
       assert_equal "method_call1 + method_call2", actual_transformed_source
 
-      source_map = ASTTransform::SourceMap.for_file_path('transformed')
+      source_map = ASTTransform::SourceMap.for_file_path("transformed")
 
       assert_equal 1, source_map.line(1)
     end
@@ -95,11 +96,11 @@ def run(node)
         method_call2
       HEREDOC
 
-      actual_transformed_source = transformer.transform_file_source(source, 'src', 'transformed')
+      actual_transformed_source = transformer.transform_file_source(source, "src", "transformed")
 
       assert_equal expected_transformed_source, actual_transformed_source
 
-      source_map = ASTTransform::SourceMap.for_file_path('transformed')
+      source_map = ASTTransform::SourceMap.for_file_path("transformed")
 
       assert_equal 1, source_map.line(1)
       assert_equal 1, source_map.line(2)
@@ -112,11 +113,11 @@ def run(node)
         method_call
       HEREDOC
 
-      transformer.transform_file_source(source, '/original/path.rb', '/transformed/path.rb')
+      transformer.transform_file_source(source, "/original/path.rb", "/transformed/path.rb")
 
-      source_map = ASTTransform::SourceMap.for_file_path('/original/path.rb')
+      source_map = ASTTransform::SourceMap.for_file_path("/original/path.rb")
       refute_nil source_map, "source map should be retrievable by source file path"
-      assert_equal '/original/path.rb', source_map.source_file_path
+      assert_equal "/original/path.rb", source_map.source_file_path
     end
 
     test "#line returns nil when transformation creates nodes that don't contain previous nodes" do
@@ -132,11 +133,11 @@ def run(node)
         method_call1 + method_call2
       HEREDOC
 
-      actual_transformed_source = transformer.transform_file_source(source, 'src', 'transformed')
+      actual_transformed_source = transformer.transform_file_source(source, "src", "transformed")
 
       assert_equal "1 + 2", actual_transformed_source
 
-      source_map = ASTTransform::SourceMap.for_file_path('transformed')
+      source_map = ASTTransform::SourceMap.for_file_path("transformed")
 
       assert_nil source_map.line(1)
     end
diff --git a/test/ast_transform/transformation_test.rb b/test/ast_transform/transformation_test.rb
index 451bd7b..43c4ba6 100644
--- a/test/ast_transform/transformation_test.rb
+++ b/test/ast_transform/transformation_test.rb
@@ -1,7 +1,8 @@
 # frozen_string_literal: true
-require 'test_helper'
-require 'transformation_helper'
-require 'ast_transform/transformation'
+
+require "test_helper"
+require "transformation_helper"
+require "ast_transform/transformation"
 
 module ASTTransform
   class TransformationTest < Minitest::Test
diff --git a/test/ast_transform/transformer_test.rb b/test/ast_transform/transformer_test.rb
index 05e4b34..db76fc8 100644
--- a/test/ast_transform/transformer_test.rb
+++ b/test/ast_transform/transformer_test.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
-require 'pathname'
-require 'test_helper'
-require 'transformation_helper'
-require 'ast_transform/abstract_transformation'
-require 'ast_transform/transformer'
+
+require "pathname"
+require "test_helper"
+require "transformation_helper"
+require "ast_transform/abstract_transformation"
+require "ast_transform/transformer"
 
 module ASTTransform
   class TransformerTest < Minitest::Test
@@ -15,6 +16,7 @@ class MethodCallToFooTransformation < ASTTransform::AbstractTransformation
 
       def process_node(node)
         return unless node.type == :send
+
         node.updated(:send, [nil, :foo])
       end
     end
@@ -24,6 +26,7 @@ class FooToBarTransformation < ASTTransform::AbstractTransformation
 
       def process_node(node)
         return unless node.type == :send && node.children == [nil, :foo]
+
         node.updated(:send, [nil, :bar])
       end
     end
@@ -33,6 +36,7 @@ class BarToFooBarTransformation < ASTTransform::AbstractTransformation
 
       def process_node(node)
         return unless node.type == :send && node.children == [nil, :bar]
+
         node.updated(:send, [nil, :foo_bar])
       end
     end
@@ -56,16 +60,16 @@ def setup
     end
 
     test "#build_ast_from_file returns the expected AST" do
-      pathname = Pathname.new('').join('tmp', 'test', 'ast_transform', 'transformer_test.rb')
+      pathname = Pathname.new("").join("tmp", "test", "ast_transform", "transformer_test.rb")
 
       FileUtils.mkdir_p(pathname.dirname)
-      File.open(pathname, 'w') do |file|
+      File.open(pathname, "w") do |file|
         file.write(@source)
       end
 
       ast = @transformer.build_ast_from_file(pathname.to_s)
 
-      assert_equal @source_ast, ast
+      assert_equal(@source_ast, ast)
     ensure
       File.delete(pathname.to_s) if File.exist?(pathname.to_s)
     end
@@ -75,37 +79,37 @@ def setup
     end
 
     test "#transform with multiple transformations" do
-      assert_equal 'foo_bar', @multi_transformer.transform(@source)
+      assert_equal "foo_bar", @multi_transformer.transform(@source)
     end
 
     test "#transform_file returns the expected transformed code" do
-      pathname = Pathname.new('').join('tmp', 'test', 'ast_transform', 'transformer_test.rb')
-      transformed_pathname = Pathname.new('').join('tmp', 'test', 'ast_transform', 'transformed_transformer_test.rb')
+      pathname = Pathname.new("").join("tmp", "test", "ast_transform", "transformer_test.rb")
+      transformed_pathname = Pathname.new("").join("tmp", "test", "ast_transform", "transformed_transformer_test.rb")
 
       FileUtils.mkdir_p(pathname.dirname)
-      File.open(pathname, 'w') do |file|
+      File.open(pathname, "w") do |file|
         file.write(@source)
       end
 
       transformed_source = @multi_transformer.transform_file(pathname.to_s, transformed_pathname.to_s)
 
-      assert_equal 'foo_bar', transformed_source
+      assert_equal("foo_bar", transformed_source)
     ensure
       File.delete(pathname.to_s) if File.exist?(pathname.to_s)
     end
 
     test "#transform_file_source returns the expected transformed code" do
-      pathname = Pathname.new('').join('tmp', 'test', 'ast_transform', 'transformer_test.rb')
-      transformed_pathname = Pathname.new('').join('tmp', 'test', 'ast_transform', 'transformed_transformer_test.rb')
+      pathname = Pathname.new("").join("tmp", "test", "ast_transform", "transformer_test.rb")
+      transformed_pathname = Pathname.new("").join("tmp", "test", "ast_transform", "transformed_transformer_test.rb")
 
       FileUtils.mkdir_p(pathname.dirname)
-      File.open(pathname, 'w') do |file|
+      File.open(pathname, "w") do |file|
         file.write(@source)
       end
 
       transformed_source = @multi_transformer.transform_file_source(@source, pathname.to_s, transformed_pathname.to_s)
 
-      assert_equal 'foo_bar', transformed_source
+      assert_equal("foo_bar", transformed_source)
     ensure
       File.delete(pathname.to_s) if File.exist?(pathname.to_s)
     end
diff --git a/test/ast_transform_test.rb b/test/ast_transform_test.rb
index 98b5c9c..612e212 100644
--- a/test/ast_transform_test.rb
+++ b/test/ast_transform_test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "test_helper"
 
 class ASTTransformTest < Minitest::Test
diff --git a/test/declarative.rb b/test/declarative.rb
index 7e9bbd6..971a898 100644
--- a/test/declarative.rb
+++ b/test/declarative.rb
@@ -1,16 +1,18 @@
 # frozen_string_literal: true
+
 # TODO: Give Credits to Rails, borrowed from ActiveSupport::Testing::Declarative
 module ASTTransform
   module Declarative
     def test(name, &block)
-      test_name = "test_#{name.gsub(/\s+/, '_')}".to_sym
-      defined = method_defined? test_name
+      test_name = "test_#{name.gsub(/\s+/, "_")}".to_sym
+      defined = method_defined?(test_name)
       raise "#{test_name} is already defined in #{self}" if defined
+
       if block_given?
         define_method(test_name, &block)
       else
         define_method(test_name) do
-          flunk "No implementation provided for #{name}"
+          flunk("No implementation provided for #{name}")
         end
       end
     end
diff --git a/test/minitest/reporters/rake_rerun_reporter.rb b/test/minitest/reporters/rake_rerun_reporter.rb
index 896d25f..85a5c43 100644
--- a/test/minitest/reporters/rake_rerun_reporter.rb
+++ b/test/minitest/reporters/rake_rerun_reporter.rb
@@ -1,11 +1,11 @@
 # frozen_string_literal: true
-require 'minitest/reporters'
-require 'ast_transform/source_map'
+
+require "minitest/reporters"
+require "ast_transform/source_map"
 
 module Minitest
   module Reporters
     class RakeRerunReporter < Minitest::Reporters::ProgressReporter
-
       def initialize(options = {})
         @rerun_user_prefix = options.fetch(:rerun_prefix, "")
         super
@@ -26,7 +26,7 @@ def record(test)
 
       def print_rerun_command(test)
         message = rerun_message_for(test)
-        unless message.nil? || message.strip == ''
+        unless message.nil? || message.strip == ""
           puts
           puts yellow(message)
         end
@@ -39,15 +39,16 @@ def rerun_message_for(test)
       end
 
       def location(exception)
-        last_before_assertion = ''
+        last_before_assertion = ""
 
         exception.backtrace.reverse_each do |ss|
           break if ss =~ /in .(assert|refute|flunk|pass|fail|raise|must|wont)/
+
           last_before_assertion = ss
           break if ss =~ /_test.rb\:/
         end
 
-        last_before_assertion.sub(/:in .*$/, '')
+        last_before_assertion.sub(/:in .*$/, "")
       end
     end
   end
diff --git a/test/string_helper.rb b/test/string_helper.rb
index a1ca0dc..cfbec1d 100644
--- a/test/string_helper.rb
+++ b/test/string_helper.rb
@@ -4,7 +4,7 @@ module ASTTransform
   module Helpers
     module StringHelper
       def strip_end_line(str)
-        str.gsub(/\n$/, '')
+        str.gsub(/\n$/, "")
       end
     end
   end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 5d1c532..2df118c 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -1,4 +1,6 @@
-$LOAD_PATH.unshift File.expand_path("../../lib", __FILE__)
+# frozen_string_literal: true
+
+$LOAD_PATH.unshift(File.expand_path("../../lib", __FILE__))
 require "ast_transform"
 
 require "declarative"
@@ -6,7 +8,7 @@
 # Minitest
 begin
   require "rubygems"
-  gem "minitest"
+  gem("minitest")
 rescue Gem::LoadError
   # do nothing
 end
@@ -21,4 +23,4 @@
 require "minitest/reporters/rake_rerun_reporter"
 Minitest::Reporters.use!([Minitest::Reporters::RakeRerunReporter.new])
 
-Minitest.autorun
\ No newline at end of file
+Minitest.autorun
diff --git a/test/test_loader.rb b/test/test_loader.rb
index 9f8539d..a045b1e 100644
--- a/test/test_loader.rb
+++ b/test/test_loader.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
-require 'simplecov'
-require 'simplecov_json_formatter'
+
+require "simplecov"
+require "simplecov_json_formatter"
 
 SimpleCov.start do
-  add_filter('/test/')
+  add_filter("/test/")
   formatter SimpleCov::Formatter::MultiFormatter.new([
     SimpleCov::Formatter::HTMLFormatter,
     SimpleCov::Formatter::JSONFormatter,
@@ -15,6 +16,6 @@
 
 # Pry
 # NOTE: Must be loaded before ASTTransform.install, otherwise we get a bunch of require_relative errors
-require 'pry'
+require "pry"
 
 ASTTransform.install
diff --git a/test/transformation_helper.rb b/test/transformation_helper.rb
index 46ffd23..6af5e70 100644
--- a/test/transformation_helper.rb
+++ b/test/transformation_helper.rb
@@ -1,7 +1,8 @@
 # frozen_string_literal: true
-require 'ast_transform/transformer'
-require 'ast_transform/transformation_helper'
-require 'string_helper'
+
+require "ast_transform/transformer"
+require "ast_transform/transformation_helper"
+require "string_helper"
 
 module ASTTransform
   module Helpers