diff --git a/.gitignore b/.gitignore
index 5e8900e..5d5a18c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,4 @@
 /tmp/
 /vendor/bundle/
 /node_modules/
+/.rubocop-*
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..59497f4
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,45 @@
+inherit_from:
+  - https://github.com/onk/onkcop/raw/v0.51.0.0/config/rubocop.yml
+
+AllCops:
+  TargetRubyVersion: 2.2
+  Exclude:
+    - 'bin/**/*'
+
+# TODO: Remove this config after droping Ruby 2.2 support
+Layout/IndentHeredoc:
+  Include:
+    - 'test/**/*'
+
+Lint/AssignmentInCondition:
+  Enabled: false
+
+Lint/HandleExceptions:
+  Enabled: false
+
+Naming/HeredocDelimiterNaming:
+  Enabled: false
+
+Style/BlockDelimiters:
+  Enabled: false
+
+Style/MultilineBlockChain:
+  Enabled: false
+
+Style/Semicolon:
+  Enabled: false
+
+Metrics/AbcSize:
+  Max: 50
+
+Metrics/BlockLength:
+  Max: 30
+
+Metrics/MethodLength:
+  Max: 40
+
+Metrics/ModuleLength:
+  Enabled: false
+
+Metrics/LineLength:
+  Max: 200
diff --git a/Gemfile b/Gemfile
index 8fbd55c..1a9efaa 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,7 +1,7 @@
-source 'https://rubygems.org'
+source "https://rubygems.org"
 
 # Specify your gem's dependencies in language_server.gemspec
 gemspec
 
 # TODO: Use released gem after new release includes https://github.com/bbatsov/rubocop/pull/4987
-gem 'rubocop', git: 'https://github.com/bbatsov/rubocop'
+gem "rubocop", git: "https://github.com/bbatsov/rubocop"
diff --git a/Guardfile b/Guardfile
index 4b43f34..890a941 100644
--- a/Guardfile
+++ b/Guardfile
@@ -5,5 +5,5 @@ guard :minitest, all_after_pass: true do
   watch(%r{^test/(.*)\/?test_(.*)\.rb$})
   watch(%r{^test/(.*)\/?(.*)_test\.rb$})
   watch(%r{^lib/(.*/)?([^/]+)\.rb$})     { |m| "test/#{m[1]}test_#{m[2]}.rb" }
-  watch(%r{^test/test_helper\.rb$})      { 'test' }
+  watch(%r{^test/test_helper\.rb$})      { "test" }
 end
diff --git a/Rakefile b/Rakefile
index d6c5113..d433a1e 100644
--- a/Rakefile
+++ b/Rakefile
@@ -4,7 +4,7 @@ require "rake/testtask"
 Rake::TestTask.new(:test) do |t|
   t.libs << "test"
   t.libs << "lib"
-  t.test_files = FileList['test/**/*_test.rb']
+  t.test_files = FileList["test/**/*_test.rb"]
 end
 
 task :default => :test
diff --git a/benchmark/rubocop b/benchmark/rubocop
index 058dd16..ee788c7 100755
--- a/benchmark/rubocop
+++ b/benchmark/rubocop
@@ -1,8 +1,8 @@
 #!/usr/bin/env ruby
 
-require 'bundler/setup'
-require 'benchmark/ips'
-require 'language_server'
+require "bundler/setup"
+require "benchmark/ips"
+require "language_server"
 
 error_code = <<-EOS
 require "foo
@@ -13,7 +13,7 @@ a = 1
 EOS
 valid_code = File.read(__FILE__)
 
-require 'pry-byebug'
+require "pry-byebug"
 
 LanguageServer::Linter::Rubocop.new(valid_code).call
 Benchmark.ips do |x|
diff --git a/benchmark/ruby_wc b/benchmark/ruby_wc
index 8191a61..5a16a7f 100755
--- a/benchmark/ruby_wc
+++ b/benchmark/ruby_wc
@@ -1,8 +1,8 @@
 #!/usr/bin/env ruby
 
-require 'bundler/setup'
-require 'benchmark/ips'
-require 'language_server'
+require "bundler/setup"
+require "benchmark/ips"
+require "language_server"
 
 error_code = <<-EOS
 require "foo
diff --git a/bin/ci b/bin/ci
new file mode 100755
index 0000000..f388e78
--- /dev/null
+++ b/bin/ci
@@ -0,0 +1,7 @@
+#!/usr/bin/env sh
+
+set -ex
+
+bin/setup
+bin/rubocop
+bin/m
diff --git a/bin/rubocop b/bin/rubocop
new file mode 100755
index 0000000..ccb4d56
--- /dev/null
+++ b/bin/rubocop
@@ -0,0 +1,17 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+#
+# This file was generated by Bundler.
+#
+# The application 'rubocop' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "pathname"
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
+  Pathname.new(__FILE__).realpath)
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("rubocop", "rubocop")
diff --git a/circle.yml b/circle.yml
index 4007e84..d43f0c6 100644
--- a/circle.yml
+++ b/circle.yml
@@ -20,8 +20,7 @@ jobs:
             docker cp . project:/app
             docker start project
             docker-compose build $SERVICE_NAME
-      - run: docker-compose run $SERVICE_NAME bin/setup
-      - run: docker-compose run $SERVICE_NAME bin/m
+      - run: docker-compose run $SERVICE_NAME bin/ci
   test-2-3:
     <<: *test
     docker:
diff --git a/language_server.gemspec b/language_server.gemspec
index 74e2876..58b4248 100644
--- a/language_server.gemspec
+++ b/language_server.gemspec
@@ -1,7 +1,7 @@
-# coding: utf-8
-lib = File.expand_path('../lib', __FILE__)
+
+lib = File.expand_path("../lib", __FILE__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
-require 'language_server/version'
+require "language_server/version"
 
 Gem::Specification.new do |spec|
   spec.name          = "language_server"
@@ -9,8 +9,8 @@ Gem::Specification.new do |spec|
   spec.authors       = ["Fumiaki MATSUSHIMA"]
   spec.email         = ["mtsmfm@gmail.com"]
 
-  spec.summary       = %q{A Ruby Language Server implementation}
-  spec.description   = %q{A Ruby Language Server implementation}
+  spec.summary       = "A Ruby Language Server implementation"
+  spec.description   = "A Ruby Language Server implementation"
   spec.homepage      = "https://github.com/mtsmfm/language_server-ruby"
   spec.license       = "MIT"
 
@@ -19,24 +19,24 @@ Gem::Specification.new do |spec|
       f.match(%r{^(test|spec|features)/})
     end
   rescue
-    Dir.glob("**/*").reject {|path| File.directory?(path) }
+    Dir.glob("**/*").reject { |path| File.directory?(path) }
   end
   spec.bindir        = "exe"
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "rcodetools"
   spec.add_dependency "language_server-protocol", "0.4.0"
+  spec.add_dependency "rcodetools"
 
+  spec.add_development_dependency "awesome_print"
+  spec.add_development_dependency "benchmark-ips"
   spec.add_development_dependency "bundler", "~> 1.14"
-  spec.add_development_dependency "rake", "~> 10.0"
-  spec.add_development_dependency "minitest", "~> 5.0"
   spec.add_development_dependency "guard"
   spec.add_development_dependency "guard-minitest"
+  spec.add_development_dependency "m"
+  spec.add_development_dependency "minitest", "~> 5.0"
   spec.add_development_dependency "minitest-color"
-  spec.add_development_dependency "pry-byebug"
   spec.add_development_dependency "minitest-power_assert"
-  spec.add_development_dependency "m"
-  spec.add_development_dependency "awesome_print"
-  spec.add_development_dependency "benchmark-ips"
+  spec.add_development_dependency "pry-byebug"
+  spec.add_development_dependency "rake", "~> 10.0"
 end
diff --git a/lib/language_server.rb b/lib/language_server.rb
index 59db621..3d36dc1 100644
--- a/lib/language_server.rb
+++ b/lib/language_server.rb
@@ -37,16 +37,14 @@ def notify(method:, params: {})
 
         method = request[:method].to_sym
 
-        _, subscriber = subscribers.find {|k, _|
-          k === method
-        }
+        subscriber = subscribers[method]
 
         if subscriber
           keys = subscriber.parameters.map(&:last)
           result = subscriber.call(
             {
               request: request, notifier: writer.method(:notify), variables: variables
-            }.merge(variables).select {|k, _| keys.include?(k) }
+            }.merge(variables).select { |k, _| keys.include?(k) },
           )
 
           if request[:id]
@@ -74,14 +72,14 @@ def on(method, &callback)
     Protocol::Interface::InitializeResult.new(
       capabilities: Protocol::Interface::ServerCapabilities.new(
         text_document_sync: Protocol::Interface::TextDocumentSyncOptions.new(
-          change: Protocol::Constant::TextDocumentSyncKind::FULL
+          change: Protocol::Constant::TextDocumentSyncKind::FULL,
         ),
         completion_provider: Protocol::Interface::CompletionOptions.new(
           resolve_provider: true,
-          trigger_characters: %w(.)
+          trigger_characters: %w[.],
         ),
-        definition_provider: true
-      )
+        definition_provider: true,
+      ),
     )
   end
 
@@ -103,13 +101,13 @@ def on(method, &callback)
         range: Protocol::Interface::Range.new(
           start: Protocol::Interface::Position.new(
             line: error.line_num,
-            character: 0
+            character: 0,
           ),
           end: Protocol::Interface::Position.new(
             line: error.line_num,
-            character: 0
-          )
-        )
+            character: 0,
+          ),
+        ),
       )
     end
 
@@ -117,8 +115,8 @@ def on(method, &callback)
       method: :"textDocument/publishDiagnostics",
       params: Protocol::Interface::PublishDiagnosticsParams.new(
         uri: uri,
-        diagnostics: diagnostics
-      )
+        diagnostics: diagnostics,
+      ),
     )
   end
 
@@ -128,7 +126,7 @@ def on(method, &callback)
 
     [
       CompletionProvider::AdHoc.new(uri: uri, line: line, character: character, project: project),
-      CompletionProvider::Rcodetools.new(uri: uri, line: line, character: character, file_store: file_store)
+      CompletionProvider::Rcodetools.new(uri: uri, line: line, character: character, file_store: file_store),
     ].flat_map(&:call)
   end
 
diff --git a/lib/language_server/completion_provider/ad_hoc.rb b/lib/language_server/completion_provider/ad_hoc.rb
index d0e55dd..bdcb0a2 100644
--- a/lib/language_server/completion_provider/ad_hoc.rb
+++ b/lib/language_server/completion_provider/ad_hoc.rb
@@ -11,35 +11,35 @@ def initialize(uri:, line:, character:, project:)
       end
 
       def call
-        (project.constants(uri: uri, line: line, character: character).map {|c|
+        (project.constants(uri: uri, line: line, character: character).map { |c|
           Protocol::Interface::CompletionItem.new(
             label: c.name,
             detail: c.full_name,
             documentation: "#{c.remote_path}##{c.lineno}",
-            kind: Protocol::Constant::CompletionItemKind::ENUM
+            kind: Protocol::Constant::CompletionItemKind::ENUM,
           )
         } +
-        project.classes(uri: uri, line: line, character: character).map {|c|
+        project.classes(uri: uri, line: line, character: character).map { |c|
           Protocol::Interface::CompletionItem.new(
             label: c.name,
             detail: c.full_name,
             documentation: "#{c.remote_path}##{c.lineno}",
-            kind: Protocol::Constant::CompletionItemKind::CLASS
+            kind: Protocol::Constant::CompletionItemKind::CLASS,
           )
         } +
-        project.modules(uri: uri, line: line, character: character).map {|m|
+        project.modules(uri: uri, line: line, character: character).map { |m|
           Protocol::Interface::CompletionItem.new(
             label: m.name,
             detail: m.full_name,
             documentation: "#{m.remote_path}##{m.lineno}",
-            kind: Protocol::Constant::CompletionItemKind::MODULE
+            kind: Protocol::Constant::CompletionItemKind::MODULE,
           )
         }).uniq(&:label)
       end
 
       private
 
-      attr_reader :uri, :line, :character, :project
+        attr_reader :uri, :line, :character, :project
     end
   end
 end
diff --git a/lib/language_server/completion_provider/rcodetools.rb b/lib/language_server/completion_provider/rcodetools.rb
index 1cdaaf3..afbcbbf 100644
--- a/lib/language_server/completion_provider/rcodetools.rb
+++ b/lib/language_server/completion_provider/rcodetools.rb
@@ -28,16 +28,16 @@ def call
           Protocol::Interface::CompletionItem.new(
             label: method_name,
             detail: description,
-            kind: Protocol::Constant::CompletionItemKind::METHOD
+            kind: Protocol::Constant::CompletionItemKind::METHOD,
           )
         end
       end
 
       private
 
-      def source
-        @file_store.read_remote_uri(@uri)
-      end
+        def source
+          @file_store.read_remote_uri(@uri)
+        end
     end
   end
 end
diff --git a/lib/language_server/definition_provider/ad_hoc.rb b/lib/language_server/definition_provider/ad_hoc.rb
index 0c86d1a..1116109 100644
--- a/lib/language_server/definition_provider/ad_hoc.rb
+++ b/lib/language_server/definition_provider/ad_hoc.rb
@@ -15,20 +15,20 @@ def call
             range: Protocol::Interface::Range.new(
               start: Protocol::Interface::Position.new(
                 line: n.lines.begin,
-                character: 0
+                character: 0,
               ),
               end: Protocol::Interface::Position.new(
                 line: n.lines.end,
-                character: 0
-              )
-            )
+                character: 0,
+              ),
+            ),
           )
         end
       end
 
       private
 
-      attr_reader :uri, :line, :character, :project
+        attr_reader :uri, :line, :character, :project
     end
   end
 end
diff --git a/lib/language_server/file_store.rb b/lib/language_server/file_store.rb
index e956458..696f739 100644
--- a/lib/language_server/file_store.rb
+++ b/lib/language_server/file_store.rb
@@ -64,36 +64,36 @@ def read_remote_uri(remote_uri)
 
     def each(&block)
       all_paths.each do |path|
-        block.call(read(path), path)
+        yield(read(path), path)
       end
     end
 
     private
 
-    attr_reader :load_paths, :remote_root, :local_root
+      attr_reader :load_paths, :remote_root, :local_root
 
-    def all_paths
-      (cache_store.keys + load_paths.flat_map {|path|
-        Dir.glob(File.join(path, "**", "*.rb"))
-      }.map {|path|
-        FilePath.new(local_root: local_root, remote_root: remote_root, local_path: path)
-      }).uniq
-    end
+      def all_paths
+        (cache_store.keys + load_paths.flat_map { |path|
+          Dir.glob(File.join(path, "**", "*.rb"))
+        }.map { |path|
+          FilePath.new(local_root: local_root, remote_root: remote_root, local_path: path)
+        }).uniq
+      end
 
-    def exists_on_cache?(path)
-      cache_store.key?(path)
-    end
+      def exists_on_cache?(path)
+        cache_store.has_key?(path)
+      end
 
-    def read_from_cache(path)
-      cache_store[path]
-    end
+      def read_from_cache(path)
+        cache_store[path]
+      end
 
-    def read_from_local(path)
-      File.read(path.local_path)
-    end
+      def read_from_local(path)
+        File.read(path.local_path)
+      end
 
-    def cache_store
-      @cache_store ||= {}
-    end
+      def cache_store
+        @cache_store ||= {}
+      end
   end
 end
diff --git a/lib/language_server/linter/rubocop.rb b/lib/language_server/linter/rubocop.rb
index ccbeb18..897c67e 100644
--- a/lib/language_server/linter/rubocop.rb
+++ b/lib/language_server/linter/rubocop.rb
@@ -1,22 +1,21 @@
 begin
-  require 'rubocop'
+  require "rubocop"
 rescue LoadError
 end
 
 module LanguageServer
   module Linter
     class Rubocop
-      def initialize(source, config_path="")
+      def initialize(source, config_path = "")
         @source = source
         @config_path = config_path
       end
 
-
       def call
         return [] unless defined? ::RuboCop
         args = []
-        args += ["--config", @config_path] if @config_path != ''
-        args += ["--format", "json","--stdin", "lsp_buffer.rb"]
+        args += ["--config", @config_path] if @config_path != ""
+        args += ["--format", "json", "--stdin", "lsp_buffer.rb"]
         o = nil
         begin
           $stdin = StringIO.new(@source)
@@ -32,24 +31,23 @@ def call
           $stdout = STDOUT
         end
         return [] unless o
-        JSON
-          .parse(o)['files'].map { |v| v['offenses'] }
-          .flatten
-          .map { |v| Error.new(line_num: v['location']['line'].to_i - 1, message: v['message'], type: convert_type(v['severity'])) }
+        JSON.
+          parse(o)["files"].map { |v| v["offenses"] }.
+          flatten.
+          map { |v| Error.new(line_num: v["location"]["line"].to_i - 1, message: v["message"], type: convert_type(v["severity"])) }
       end
 
       private
 
-      def convert_type(type)
-        case type
-        when 'refactor' then 'warning'
-        when 'convention' then 'warning'
-        when 'warning' then 'warning'
-        when 'error' then 'error'
-        when 'fatal' then 'error'
+        def convert_type(type)
+          case type
+          when "refactor" then "warning"
+          when "convention" then "warning"
+          when "warning" then "warning"
+          when "error" then "error"
+          when "fatal" then "error"
+          end
         end
-      end
-
     end
   end
 end
diff --git a/lib/language_server/linter/ruby_wc.rb b/lib/language_server/linter/ruby_wc.rb
index 9588c4a..dfcfa56 100644
--- a/lib/language_server/linter/ruby_wc.rb
+++ b/lib/language_server/linter/ruby_wc.rb
@@ -26,55 +26,55 @@ def initialize(source)
       end
 
       def call
-        error_message.scan(/.+:(\d+):\s*(.+?)[,:]\s(.+)/).map do |line_num, type,  message|
+        error_message.scan(/.+:(\d+):\s*(.+?)[,:]\s(.+)/).map do |line_num, type, message|
           Error.new(line_num: line_num.to_i - 1, message: message, type: type)
         end
       end
 
       private
 
-      # Since Ruby 2.4, syntax error information is outputted to Exception#message instead of stderr
-      if begin; stderr = $stderr; $stderr = StringIO.new; RubyVM::InstructionSequence.compile('='); rescue SyntaxError => e; e.message != 'compile error'; ensure; $stderr = stderr; end
-        def error_message
-          with_verbose do
-            begin
-              capture_stderr { RubyVM::InstructionSequence.compile(@source) }
-            rescue SyntaxError => e
-              e.message
+        # Since Ruby 2.4, syntax error information is outputted to Exception#message instead of stderr
+        if begin; stderr = $stderr; $stderr = StringIO.new; RubyVM::InstructionSequence.compile("="); rescue SyntaxError => e; e.message != "compile error"; ensure; $stderr = stderr; end
+          def error_message
+            with_verbose do
+              begin
+                capture_stderr { RubyVM::InstructionSequence.compile(@source) }
+              rescue SyntaxError => e
+                e.message
+              end
             end
           end
-        end
-      else
-        def error_message
-          with_verbose do
-            capture_stderr do
-              begin
-                RubyVM::InstructionSequence.compile(@source)
-              rescue SyntaxError
+        else
+          def error_message
+            with_verbose do
+              capture_stderr do
+                begin
+                  RubyVM::InstructionSequence.compile(@source)
+                rescue SyntaxError
+                end
               end
             end
           end
         end
-      end
 
-      def with_verbose
-        origin = $VERBOSE
-        $VERBOSE = true
-        yield
-      ensure
-        $VERBOSE = origin
-      end
+        def with_verbose
+          origin = $VERBOSE
+          $VERBOSE = true
+          yield
+        ensure
+          $VERBOSE = origin
+        end
 
-      def capture_stderr
-        origin = $stderr
-        $stderr = StringIO.new
+        def capture_stderr
+          origin = $stderr
+          $stderr = StringIO.new
 
-        yield
+          yield
 
-        $stderr.string
-      ensure
-        $stderr = origin
-      end
+          $stderr.string
+        ensure
+          $stderr = origin
+        end
     end
   end
 end
diff --git a/lib/language_server/logger.rb b/lib/language_server/logger.rb
index e2793ca..936e671 100644
--- a/lib/language_server/logger.rb
+++ b/lib/language_server/logger.rb
@@ -1,4 +1,4 @@
-require 'logger'
+require "logger"
 
 module LanguageServer
   class << self
@@ -8,16 +8,16 @@ def logger
   end
 
   class Formatter
-    RESET = "\e[0m"
-    RED = "\e[31m"
-    YELLOW = "\e[33m"
+    RESET = "\e[0m".freeze
+    RED = "\e[31m".freeze
+    YELLOW = "\e[33m".freeze
 
     def call(severity, *rest)
       msg = default_message(severity, *rest)
       case severity
-      when 'ERROR'
+      when "ERROR"
         RED + msg + RESET
-      when 'WARN'
+      when "WARN"
         YELLOW + msg + RESET
       else
         msg
@@ -26,12 +26,12 @@ def call(severity, *rest)
 
     private
 
-    def default_message(*args)
-      default_formatter.call(*args)
-    end
+      def default_message(*args)
+        default_formatter.call(*args)
+      end
 
-    def default_formatter
-      @default_formatter ||= ::Logger::Formatter.new
-    end
+      def default_formatter
+        @default_formatter ||= ::Logger::Formatter.new
+      end
   end
 end
diff --git a/lib/language_server/project.rb b/lib/language_server/project.rb
index 8779cd3..3d91974 100644
--- a/lib/language_server/project.rb
+++ b/lib/language_server/project.rb
@@ -1,4 +1,4 @@
-require 'language_server/project/parser'
+require "language_server/project/parser"
 
 module LanguageServer
   class Project
@@ -12,11 +12,11 @@ def initialize(file_store)
     def find_definitions(uri:, line:, character:)
       result = result_store[file_store.path_from_remote_uri(uri)]
 
-      ref = result.refs.select {|node| node.lines.include?(line) && node.characters.include?(character) }.min_by {|node| node.characters.size }
+      ref = result.refs.select { |node| node.lines.include?(line) && node.characters.include?(character) }.min_by { |node| node.characters.size }
 
       return [] unless ref
 
-      lazy_modules.select {|n| n.full_name == ref.full_name }.force + lazy_classes.select {|n| n.full_name == ref.full_name }.force
+      lazy_modules.select { |n| n.full_name == ref.full_name }.force + lazy_classes.select { |n| n.full_name == ref.full_name }.force
     end
 
     def recalculate_result(uri)
@@ -27,58 +27,58 @@ def recalculate_result(uri)
     def constants(uri: nil, line: nil, character: nil)
       node = find_nearest_node(uri: uri, line: line, character: character) if uri && line && character
 
-      lazy_constants.select {|n| n.names[0..-2] == Array(node && node.names).first(n.names.size - 1) }.force
+      lazy_constants.select { |n| n.names[0..-2] == Array(node && node.names).first(n.names.size - 1) }.force
     end
 
     def modules(uri: nil, line: nil, character: nil)
       node = find_nearest_node(uri: uri, line: line, character: character) if uri && line && character
 
-      lazy_modules.select {|n| n.names[0..-2] == Array(node && node.names).first(n.names.size - 1) }.force
+      lazy_modules.select { |n| n.names[0..-2] == Array(node && node.names).first(n.names.size - 1) }.force
     end
 
     def classes(uri: nil, line: nil, character: nil)
       node = find_nearest_node(uri: uri, line: line, character: character) if uri && line && character
 
-      lazy_classes.select {|n| n.names[0..-2] == Array(node && node.names).first(n.names.size - 1) }.force
+      lazy_classes.select { |n| n.names[0..-2] == Array(node && node.names).first(n.names.size - 1) }.force
     end
 
     private
 
-    attr_reader :file_store, :result_store
+      attr_reader :file_store, :result_store
 
-    def lazy_constants
-      result_store.each_value.lazy.flat_map(&:constants)
-    end
-
-    def lazy_modules
-      result_store.each_value.lazy.flat_map(&:modules)
-    end
+      def lazy_constants
+        result_store.each_value.lazy.flat_map(&:constants)
+      end
 
-    def lazy_classes
-      result_store.each_value.lazy.flat_map(&:classes)
-    end
+      def lazy_modules
+        result_store.each_value.lazy.flat_map(&:modules)
+      end
 
-    def fetch_result
-      file_store.each {|content, path|
-        calculate(content, path)
-      }
-    end
+      def lazy_classes
+        result_store.each_value.lazy.flat_map(&:classes)
+      end
 
-    def find_nearest_node(uri:, line:, character:)
-      result = result_store[file_store.path_from_remote_uri(uri)]
+      def fetch_result
+        file_store.each { |content, path|
+          calculate(content, path)
+        }
+      end
 
-      (result.modules + result.classes).select {|node| node.lines.include?(line) }.min_by {|node| node.lines.size }
-    end
+      def find_nearest_node(uri:, line:, character:)
+        result = result_store[file_store.path_from_remote_uri(uri)]
 
-    def calculate(content, path)
-      begin
-        result = Parser.parse(content, path)
-      rescue => e
-        LanguageServer.logger.warn("Parse failed (local: #{path.local_path}, remote: #{path.remote_path})")
-        LanguageServer.logger.warn(e)
+        (result.modules + result.classes).select { |node| node.lines.include?(line) }.min_by { |node| node.lines.size }
       end
 
-      result_store[path] = result if result
-    end
+      def calculate(content, path)
+        begin
+          result = Parser.parse(content, path)
+        rescue => e
+          LanguageServer.logger.warn("Parse failed (local: #{path.local_path}, remote: #{path.remote_path})")
+          LanguageServer.logger.warn(e)
+        end
+
+        result_store[path] = result if result
+      end
   end
 end
diff --git a/lib/language_server/project/node.rb b/lib/language_server/project/node.rb
index b6f9222..fbae995 100644
--- a/lib/language_server/project/node.rb
+++ b/lib/language_server/project/node.rb
@@ -6,12 +6,10 @@ def attributes(*attrs)
           attr_accessor(*attrs)
           attribute_names.concat(attrs)
           class_eval <<-RUBY, __FILE__, __LINE__
-def initialize(#{attribute_names.map {|n| "#{n}:" }.join(',')})
-  #{
-    attribute_names.map {|n|
+def initialize(#{attribute_names.map { |n| "#{n}:" }.join(",")})
+  #{attribute_names.map { |n|
       "@#{n} = #{n}"
-    }.join("\n")
-  }
+    }.join("\n")}
 end
           RUBY
         end
@@ -23,8 +21,13 @@ def attribute_names
 
       attributes :lineno, :character, :path
 
-      def remote_path; path.remote_path; end
-      def local_path;  path.local_path;  end
+      def remote_path
+        path.remote_path
+      end
+
+      def local_path
+        path.local_path
+      end
 
       def eql?(other)
         other.instance_of?(self.class) && attributes == other.attributes
@@ -39,7 +42,7 @@ def hash
       end
 
       def attributes
-        self.class.attribute_names.map {|a|
+        self.class.attribute_names.map { |a|
           [a, public_send(a)]
         }.to_h
       end
@@ -57,7 +60,7 @@ def names
       end
 
       def full_name
-        names.join('::')
+        names.join("::")
       end
     end
 
@@ -68,7 +71,7 @@ class LiteralValue < Node
     class Module < Node
       attributes :constant, :children
 
-      %i(name namespaces full_name names).each do |m|
+      %i[name namespaces full_name names].each do |m|
         define_method(m) { constant.__send__(m) }
       end
 
@@ -117,7 +120,7 @@ def name
       end
 
       def full_name
-        names.join('::')
+        names.join("::")
       end
 
       def inspect
@@ -149,7 +152,7 @@ def names
       end
 
       def full_name
-        names.join('::')
+        names.join("::")
       end
 
       def inspect
diff --git a/lib/language_server/project/parser.rb b/lib/language_server/project/parser.rb
index 8e1de01..03d58d5 100644
--- a/lib/language_server/project/parser.rb
+++ b/lib/language_server/project/parser.rb
@@ -1,5 +1,5 @@
-require 'language_server/project/node'
-require 'ripper'
+require "language_server/project/node"
+require "ripper"
 
 module LanguageServer
   class Project
@@ -32,79 +32,79 @@ def initialize(src, path)
 
       private
 
-      alias character column
+        alias_method :character, :column
 
-      attr_reader :path
+        attr_reader :path
 
-      def lineno
-        # Language Server Protocol's lineno is zero origin
-        super - 1
-      end
+        def lineno
+          # Language Server Protocol's lineno is zero origin
+          super - 1
+        end
 
-      def on_var_ref(node)
-        if node.instance_of?(Constant)
-          build_node(VarRef, node: node).tap do |n|
-            result.refs << n
+        def on_var_ref(node)
+          if node.instance_of?(Constant)
+            build_node(VarRef, node: node).tap do |n|
+              result.refs << n
+            end
+          else
+            node
           end
-        else
-          node
         end
-      end
 
-      def on_const_path_ref(*nodes)
-        if nodes.all? {|n| [Constant, ConstPathRef, VarRef].include?(n.class) }
-          build_node(ConstPathRef, nodes: nodes).tap do |n|
-            result.refs << n
+        def on_const_path_ref(*nodes)
+          if nodes.all? { |n| [Constant, ConstPathRef, VarRef].include?(n.class) }
+            build_node(ConstPathRef, nodes: nodes).tap do |n|
+              result.refs << n
+            end
+          else
+            nodes
           end
-        else
-          nodes
         end
-      end
 
-      def on_const(name)
-        build_node(Constant, namespaces: [], name: name, value: nil)
-      end
+        def on_const(name)
+          build_node(Constant, namespaces: [], name: name, value: nil)
+        end
 
-      def on_def(*args)
-        args.flatten.compact
-      end
+        def on_def(*args)
+          args.flatten.compact
+        end
 
-      def on_int(value)
-        build_node(LiteralValue, value: value.to_i)
-      end
+        def on_int(value)
+          build_node(LiteralValue, value: value.to_i)
+        end
 
-      def on_stmts_add(*args)
-        args.flatten.compact
-      end
+        def on_stmts_add(*args)
+          args.flatten.compact
+        end
 
-      def on_assign(left, right)
-        result.constants << left if Constant === left
+        def on_assign(left, right)
+          result.constants << left if left.instance_of?(Constant)
 
-        left.value = right if left.respond_to?(:value) # TODO: remove this condition
-        left
-      end
+          left.value = right if left.respond_to?(:value) # TODO: remove this condition
+          left
+        end
 
-      def on_module(constant, children)
-        cn = children.select {|child| child.respond_to?(:unshift_namespace) }
+        def on_module(constant, children)
+          cn = children.select { |child| child.respond_to?(:unshift_namespace) }
 
-        build_node(Module, constant: constant, children: cn).tap do |m|
-          result.modules << m
-          cn.each {|child| child.unshift_namespace(m) }
+          build_node(Module, constant: constant, children: cn).tap do |m|
+            result.modules << m
+            cn.each { |child| child.unshift_namespace(m) }
+          end
         end
-      end
 
-      def on_class(constant, superclass, children)
-        cn = children.select {|child| child.respond_to?(:unshift_namespace) }
+        def on_class(constant, superclass, children)
+          cn = children.select { |child| child.respond_to?(:unshift_namespace) }
 
-        build_node(Class, constant: constant, superclass: superclass, children: cn).tap do |c|
-          result.classes << c
-          cn.each {|child| child.unshift_namespace(c) }
+          build_node(Class, constant: constant, superclass: superclass, children: cn).tap do |c|
+            result.classes << c
+            cn.each { |child| child.unshift_namespace(c) }
+          end
         end
-      end
 
-      def build_node(klass, **args)
-        klass.new({lineno: lineno, character: character, path: path}.merge(args))
-      end
+        def build_node(klass, **args)
+          klass.new({ lineno: lineno, character: character, path: path }.merge(args))
+        end
     end
   end
 end
diff --git a/lib/language_server/version.rb b/lib/language_server/version.rb
index 7f17d09..9ed2a74 100644
--- a/lib/language_server/version.rb
+++ b/lib/language_server/version.rb
@@ -1,3 +1,3 @@
 module LanguageServer
-  VERSION = "0.9.0"
+  VERSION = "0.9.0".freeze
 end
diff --git a/test/language_server/completion_provider/rcodetools_test.rb b/test/language_server/completion_provider/rcodetools_test.rb
index a0c8332..bbd899a 100644
--- a/test/language_server/completion_provider/rcodetools_test.rb
+++ b/test/language_server/completion_provider/rcodetools_test.rb
@@ -1,4 +1,4 @@
-require 'test_helper'
+require "test_helper"
 
 module LanguageServer
   module CompletionProvider
@@ -18,7 +18,7 @@ def test_array
         candidates = [
           Protocol::Interface::CompletionItem.new(label: "last",   kind: Protocol::Constant::CompletionItemKind::METHOD, detail: "Array#last"),
           Protocol::Interface::CompletionItem.new(label: "lazy",   kind: Protocol::Constant::CompletionItemKind::METHOD, detail: "Enumerable#lazy"),
-          Protocol::Interface::CompletionItem.new(label: "length", kind: Protocol::Constant::CompletionItemKind::METHOD, detail: "Array#length")
+          Protocol::Interface::CompletionItem.new(label: "length", kind: Protocol::Constant::CompletionItemKind::METHOD, detail: "Array#length"),
         ]
 
         assert { provider.call.to_json == candidates.to_json }
diff --git a/test/language_server/linter/rubocop_test.rb b/test/language_server/linter/rubocop_test.rb
index 6673ca5..0154682 100644
--- a/test/language_server/linter/rubocop_test.rb
+++ b/test/language_server/linter/rubocop_test.rb
@@ -1,9 +1,9 @@
-require 'test_helper'
+require "test_helper"
 
 module LanguageServer::Linter
   class RubocopTest < Minitest::Test
     def setup
-      @config_path = File.expand_path('./../../../fixtures/rubocop.yml', __FILE__)
+      @config_path = File.expand_path("./../../../fixtures/rubocop.yml", __FILE__)
     end
 
     def test_fatal_error
@@ -14,8 +14,8 @@ def test_fatal_error
           Error.new(
             line_num: 0,
             message: "unterminated string meets end of file\n(Using Ruby 2.1 parser; configure using `TargetRubyVersion` parameter, under `AllCops`)",
-            type: 'error'
-          )
+            type: "error",
+          ),
         ]
       end
     end
@@ -24,7 +24,7 @@ def test_warning_error
       source = "a = 'a'"
       actual = Rubocop.new(source, @config_path).call
       assert do
-        actual.first == Error.new(line_num: 0, message: "Useless assignment to variable - `a`.", type: 'warning')
+        actual.first == Error.new(line_num: 0, message: "Useless assignment to variable - `a`.", type: "warning")
       end
     end
 
@@ -32,7 +32,7 @@ def test_convention_error
       source = 'require "foo"'
       actual = Rubocop.new(source, @config_path).call
       assert do
-        actual.first == Error.new(line_num: 0, message: "Prefer single-quoted strings when you don't need string interpolation or special symbols.", type: 'warning')
+        actual.first == Error.new(line_num: 0, message: "Prefer single-quoted strings when you don't need string interpolation or special symbols.", type: "warning")
       end
     end
   end
diff --git a/test/language_server/linter/ruby_wc_test.rb b/test/language_server/linter/ruby_wc_test.rb
index 67bfb90..7d4208b 100644
--- a/test/language_server/linter/ruby_wc_test.rb
+++ b/test/language_server/linter/ruby_wc_test.rb
@@ -1,4 +1,4 @@
-require 'test_helper'
+require "test_helper"
 
 module LanguageServer::Linter
   class RubyWCTest < Minitest::Test
diff --git a/test/language_server/project/parser_test.rb b/test/language_server/project/parser_test.rb
index 839935f..6b0ea87 100644
--- a/test/language_server/project/parser_test.rb
+++ b/test/language_server/project/parser_test.rb
@@ -1,4 +1,4 @@
-require 'test_helper'
+require "test_helper"
 
 module LanguageServer
   class Project
@@ -10,7 +10,7 @@ def test_toplevel_const
 
         result = Parser.parse(body)
 
-        assert { result.constants.map(&:full_name) == %w(TOP_LEVEL_CONST) }
+        assert { result.constants.map(&:full_name) == %w[TOP_LEVEL_CONST] }
       end
 
       def test_const_within_class_and_module
@@ -24,8 +24,8 @@ module Mod
 
         result = Parser.parse(body)
 
-        assert { result.modules.map(&:full_name) == %w(Cls::Mod) }
-        assert { result.constants.map(&:full_name) == %w(Cls::Mod::CONST) }
+        assert { result.modules.map(&:full_name) == %w[Cls::Mod] }
+        assert { result.constants.map(&:full_name) == %w[Cls::Mod::CONST] }
       end
 
       def test_class
@@ -36,7 +36,7 @@ class Hi
 
         result = Parser.parse(body)
 
-        assert { result.classes.map(&:full_name) == %w(Hi) }
+        assert { result.classes.map(&:full_name) == %w[Hi] }
       end
 
       def test_module
@@ -47,7 +47,7 @@ module Hi
 
         result = Parser.parse(body)
 
-        assert { result.modules.map(&:full_name) == %w(Hi) }
+        assert { result.modules.map(&:full_name) == %w[Hi] }
       end
 
       def test_module_with_method
@@ -60,7 +60,7 @@ def initialize
 
         result = Parser.parse(body)
 
-        assert { result.modules.map(&:full_name) == %w(Hi) }
+        assert { result.modules.map(&:full_name) == %w[Hi] }
       end
 
       def test_ref
@@ -68,7 +68,7 @@ def test_ref
           A
         EOS
 
-        assert { result.refs.map {|r| [r.full_name, r.characters] } == [['A', 0..1]] }
+        assert { result.refs.map { |r| [r.full_name, r.characters] } == [["A", 0..1]] }
       end
 
       def test_ref_2
@@ -76,7 +76,7 @@ def test_ref_2
           A::B
         EOS
 
-        assert { result.refs.map {|r| [r.full_name, r.characters] } == [['A', 0..2], ['A::B', 0..3]] }
+        assert { result.refs.map { |r| [r.full_name, r.characters] } == [["A", 0..2], ["A::B", 0..3]] }
       end
 
       def test_ref_3
@@ -84,7 +84,7 @@ def test_ref_3
           A::B::C
         EOS
 
-        assert { result.refs.map {|r| [r.full_name, r.characters] } == [['A', 0..2], ['A::B', 0..3], ['A::B::C', 0..6]] }
+        assert { result.refs.map { |r| [r.full_name, r.characters] } == [["A", 0..2], ["A::B", 0..3], ["A::B::C", 0..6]] }
       end
 
       def test_ref_within_module
@@ -94,7 +94,7 @@ module A
           end
         EOS
 
-        assert { result.refs.map {|r| [r.full_name, r.characters] } == [['A::B', 2..3]] }
+        assert { result.refs.map { |r| [r.full_name, r.characters] } == [["A::B", 2..3]] }
 
         result = Parser.parse(<<-EOS.strip_heredoc)
           module A
@@ -102,7 +102,7 @@ module A
           end
         EOS
 
-        assert { result.refs.map {|r| [r.full_name, r.characters] } == [['A::B', 2..4], ['A::B::C', 2..5]] }
+        assert { result.refs.map { |r| [r.full_name, r.characters] } == [["A::B", 2..4], ["A::B::C", 2..5]] }
       end
 
       def test_const_ref_with_method
@@ -123,7 +123,7 @@ class C::D::E
           end
         EOS
 
-        assert { result.classes.map(&:full_name) == %w(A::B::C::D::E) }
+        assert { result.classes.map(&:full_name) == %w[A::B::C::D::E] }
       end
     end
   end
diff --git a/test/language_server/project_test.rb b/test/language_server/project_test.rb
index ca7cf39..42c971c 100644
--- a/test/language_server/project_test.rb
+++ b/test/language_server/project_test.rb
@@ -1,10 +1,10 @@
-require 'test_helper'
+require "test_helper"
 
 module LanguageServer
   class ProjectTest < Minitest::Test
     def test_const_within_class_and_module
       store = FileStore.new
-      store.cache('file:///a.rb', <<-EOS.strip_heredoc)
+      store.cache("file:///a.rb", <<-EOS.strip_heredoc)
         class A
           module A
             class C
@@ -13,21 +13,21 @@ class C
         end
       EOS
 
-      store.cache('file:///b.rb', <<-EOS.strip_heredoc)
+      store.cache("file:///b.rb", <<-EOS.strip_heredoc)
         class A
           module B
           end
         end
       EOS
 
-      store.cache('file:///c.rb', <<-EOS.strip_heredoc)
+      store.cache("file:///c.rb", <<-EOS.strip_heredoc)
         class B
           module C
           end
         end
       EOS
 
-      uri = 'file:///foo.rb'
+      uri = "file:///foo.rb"
       store.cache(uri, <<-EOS.strip_heredoc)
 
         class A
@@ -40,16 +40,16 @@ def hi
 
       project = Project.new(store)
       assert { project.modules(uri: uri, line: 0, character: 0).map(&:full_name) == [] }
-      assert { project.modules(uri: uri, line: 1, character: 0).map(&:full_name).uniq.sort == %w(A::A A::B).sort }
+      assert { project.modules(uri: uri, line: 1, character: 0).map(&:full_name).uniq.sort == %w[A::A A::B].sort }
 
-      assert { project.classes(uri: uri, line: 0, character: 0).map(&:full_name).uniq.sort == %w(A B).sort }
-      assert { project.classes(uri: uri, line: 1, character: 0).map(&:full_name).uniq.sort == %w(A B).sort }
-      assert { project.classes(uri: uri, line: 2, character: 0).map(&:full_name).uniq.sort == %w(A B A::A::C).sort }
+      assert { project.classes(uri: uri, line: 0, character: 0).map(&:full_name).uniq.sort == %w[A B].sort }
+      assert { project.classes(uri: uri, line: 1, character: 0).map(&:full_name).uniq.sort == %w[A B].sort }
+      assert { project.classes(uri: uri, line: 2, character: 0).map(&:full_name).uniq.sort == %w[A B A::A::C].sort }
     end
 
     def test_find_definition
       store = FileStore.new
-      store.cache('file:///a.rb', <<-EOS.strip_heredoc)
+      store.cache("file:///a.rb", <<-EOS.strip_heredoc)
         class A
           module A
             class C
@@ -60,7 +60,7 @@ def foo
         end
       EOS
 
-      store.cache('file:///b.rb', <<-EOS.strip_heredoc)
+      store.cache("file:///b.rb", <<-EOS.strip_heredoc)
         class A
           def hi
             A::C.foo
@@ -70,8 +70,8 @@ def hi
 
       project = Project.new(store)
 
-      assert { project.find_definitions(uri: 'file:///b.rb', line: 2, character: 6).first.full_name == 'A::A' }
-      assert { project.find_definitions(uri: 'file:///b.rb', line: 2, character: 7).first.full_name == 'A::A::C' }
+      assert { project.find_definitions(uri: "file:///b.rb", line: 2, character: 6).first.full_name == "A::A" }
+      assert { project.find_definitions(uri: "file:///b.rb", line: 2, character: 7).first.full_name == "A::A::C" }
     end
   end
 end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 33f3939..17c3ede 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -1,14 +1,14 @@
-$LOAD_PATH.unshift File.expand_path('../../lib', __FILE__)
-require 'bundler'
+$LOAD_PATH.unshift File.expand_path("../../lib", __FILE__)
+require "bundler"
 Bundler.require(:default, :development)
 
-require 'minitest/autorun'
-require 'power_assert/colorize'
+require "minitest/autorun"
+require "power_assert/colorize"
 
 class String
   def strip_heredoc
     min = scan(/^[ \t]*(?=\S)/).min
     indent = min ? min.size : 0
-    gsub(/^[ \t]{#{indent}}/, '')
+    gsub(/^[ \t]{#{indent}}/, "")
   end
 end