diff --git a/.gitignore b/.gitignore
index 10aa7a7..c8e8cf2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,7 +4,6 @@
 .bundle
 .config
 .yardoc
-Gemfile.lock
 InstalledFiles
 _yardoc
 coverage
diff --git a/Gemfile b/Gemfile
index 702e422..52210ab 100644
--- a/Gemfile
+++ b/Gemfile
@@ -4,7 +4,8 @@ source 'https://rubygems.org'
 gemspec
 
 group :test do
-  gem 'rails', '~> 4.0'
+  gem 'rails', '>= 4.0'
+  gem 'sprockets', '~> 3'
   gem 'sprockets-rails', '> 2.0'
   gem 'minitest-power_assert'
   gem 'coveralls'
diff --git a/Gemfile.lock b/Gemfile.lock
new file mode 100644
index 0000000..e025d7d
--- /dev/null
+++ b/Gemfile.lock
@@ -0,0 +1,216 @@
+PATH
+  remote: .
+  specs:
+    typescript-rails (0.6.2.4)
+      railties
+      tilt
+      typescript-node (>= 1.6.2)
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    actioncable (7.0.4.3)
+      actionpack (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+      nio4r (~> 2.0)
+      websocket-driver (>= 0.6.1)
+    actionmailbox (7.0.4.3)
+      actionpack (= 7.0.4.3)
+      activejob (= 7.0.4.3)
+      activerecord (= 7.0.4.3)
+      activestorage (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+      mail (>= 2.7.1)
+      net-imap
+      net-pop
+      net-smtp
+    actionmailer (7.0.4.3)
+      actionpack (= 7.0.4.3)
+      actionview (= 7.0.4.3)
+      activejob (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+      mail (~> 2.5, >= 2.5.4)
+      net-imap
+      net-pop
+      net-smtp
+      rails-dom-testing (~> 2.0)
+    actionpack (7.0.4.3)
+      actionview (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+      rack (~> 2.0, >= 2.2.0)
+      rack-test (>= 0.6.3)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.0, >= 1.2.0)
+    actiontext (7.0.4.3)
+      actionpack (= 7.0.4.3)
+      activerecord (= 7.0.4.3)
+      activestorage (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+      globalid (>= 0.6.0)
+      nokogiri (>= 1.8.5)
+    actionview (7.0.4.3)
+      activesupport (= 7.0.4.3)
+      builder (~> 3.1)
+      erubi (~> 1.4)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.1, >= 1.2.0)
+    activejob (7.0.4.3)
+      activesupport (= 7.0.4.3)
+      globalid (>= 0.3.6)
+    activemodel (7.0.4.3)
+      activesupport (= 7.0.4.3)
+    activerecord (7.0.4.3)
+      activemodel (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+    activestorage (7.0.4.3)
+      actionpack (= 7.0.4.3)
+      activejob (= 7.0.4.3)
+      activerecord (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+      marcel (~> 1.0)
+      mini_mime (>= 1.1.0)
+    activesupport (7.0.4.3)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 1.6, < 2)
+      minitest (>= 5.1)
+      tzinfo (~> 2.0)
+    builder (3.2.4)
+    concurrent-ruby (1.2.2)
+    coveralls (0.7.1)
+      multi_json (~> 1.3)
+      rest-client
+      simplecov (>= 0.7)
+      term-ansicolor
+      thor
+    crass (1.0.6)
+    date (3.3.3)
+    docile (1.4.0)
+    domain_name (0.5.20190701)
+      unf (>= 0.0.5, < 1.0.0)
+    erubi (1.12.0)
+    globalid (1.1.0)
+      activesupport (>= 5.0)
+    http-accept (1.7.0)
+    http-cookie (1.0.5)
+      domain_name (~> 0.5)
+    i18n (1.12.0)
+      concurrent-ruby (~> 1.0)
+    loofah (2.20.0)
+      crass (~> 1.0.2)
+      nokogiri (>= 1.5.9)
+    mail (2.8.1)
+      mini_mime (>= 0.1.1)
+      net-imap
+      net-pop
+      net-smtp
+    marcel (1.0.2)
+    method_source (1.0.0)
+    mime-types (3.4.1)
+      mime-types-data (~> 3.2015)
+    mime-types-data (3.2023.0218.1)
+    mini_mime (1.1.2)
+    minitest (5.18.0)
+    minitest-power_assert (0.3.1)
+      minitest
+      power_assert (>= 1.1)
+    multi_json (1.15.0)
+    net-imap (0.3.4)
+      date
+      net-protocol
+    net-pop (0.1.2)
+      net-protocol
+    net-protocol (0.2.1)
+      timeout
+    net-smtp (0.3.3)
+      net-protocol
+    netrc (0.11.0)
+    nio4r (2.5.9)
+    nokogiri (1.14.2-x86_64-darwin)
+      racc (~> 1.4)
+    power_assert (2.0.3)
+    racc (1.6.2)
+    rack (2.2.6.4)
+    rack-test (2.1.0)
+      rack (>= 1.3)
+    rails (7.0.4.3)
+      actioncable (= 7.0.4.3)
+      actionmailbox (= 7.0.4.3)
+      actionmailer (= 7.0.4.3)
+      actionpack (= 7.0.4.3)
+      actiontext (= 7.0.4.3)
+      actionview (= 7.0.4.3)
+      activejob (= 7.0.4.3)
+      activemodel (= 7.0.4.3)
+      activerecord (= 7.0.4.3)
+      activestorage (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+      bundler (>= 1.15.0)
+      railties (= 7.0.4.3)
+    rails-dom-testing (2.0.3)
+      activesupport (>= 4.2.0)
+      nokogiri (>= 1.6)
+    rails-html-sanitizer (1.5.0)
+      loofah (~> 2.19, >= 2.19.1)
+    railties (7.0.4.3)
+      actionpack (= 7.0.4.3)
+      activesupport (= 7.0.4.3)
+      method_source
+      rake (>= 12.2)
+      thor (~> 1.0)
+      zeitwerk (~> 2.5)
+    rake (13.0.6)
+    rest-client (2.1.0)
+      http-accept (>= 1.7.0, < 2.0)
+      http-cookie (>= 1.0.2, < 2.0)
+      mime-types (>= 1.16, < 4.0)
+      netrc (~> 0.8)
+    simplecov (0.22.0)
+      docile (~> 1.1)
+      simplecov-html (~> 0.11)
+      simplecov_json_formatter (~> 0.1)
+    simplecov-html (0.12.3)
+    simplecov_json_formatter (0.1.4)
+    sprockets (3.7.2)
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
+    sprockets-rails (3.4.2)
+      actionpack (>= 5.2)
+      activesupport (>= 5.2)
+      sprockets (>= 3.0.0)
+    sync (0.5.0)
+    term-ansicolor (1.7.1)
+      tins (~> 1.0)
+    thor (1.2.1)
+    tilt (2.1.0)
+    timeout (0.3.2)
+    tins (1.32.1)
+      sync
+    typescript-node (1.6.2)
+      typescript-src (~> 1.6.2)
+    typescript-src (1.6.2.0)
+    tzinfo (2.0.6)
+      concurrent-ruby (~> 1.0)
+    unf (0.1.4)
+      unf_ext
+    unf_ext (0.0.8.2)
+    websocket-driver (0.7.5)
+      websocket-extensions (>= 0.1.0)
+    websocket-extensions (0.1.5)
+    zeitwerk (2.6.7)
+
+PLATFORMS
+  x86_64-darwin-21
+  x86_64-darwin-22
+
+DEPENDENCIES
+  coveralls
+  minitest-power_assert
+  rails (>= 4.0)
+  simplecov
+  sprockets (~> 3)
+  sprockets-rails (> 2.0)
+  typescript-rails!
+  tzinfo-data
+
+BUNDLED WITH
+   2.4.10
diff --git a/app/assets/config/manifest.js b/app/assets/config/manifest.js
new file mode 100644
index 0000000..b16e53d
--- /dev/null
+++ b/app/assets/config/manifest.js
@@ -0,0 +1,3 @@
+//= link_tree ../images
+//= link_directory ../javascripts .js
+//= link_directory ../stylesheets .css
diff --git a/lib/typescript/rails/compiler.rb b/lib/typescript/rails/compiler.rb
index 093b311..3c6cc5e 100644
--- a/lib/typescript/rails/compiler.rb
+++ b/lib/typescript/rails/compiler.rb
@@ -2,10 +2,10 @@
 require 'typescript-node'
 
 module Typescript::Rails::Compiler
-  class << self
-    # @!scope class
-    cattr_accessor :default_options
+  # @!scope class
+  self.cattr_accessor(:default_options)
 
+  class << self
     # Replace relative paths specified in /// <reference path="..." /> with absolute paths.
     #
     # @param [String] ts_path Source .ts path
@@ -18,7 +18,7 @@ def replace_relative_references(ts_path, source)
       # Why don't we just use gsub? Because it display odd behavior with File.join on Ruby 2.0
       # So we go the long way around.
       (source.each_line.map do |l|
-        if l.starts_with?('///') && !(m = %r!^///\s*<reference\s+path=(?:"([^"]+)"|'([^']+)')\s*/>\s*!.match(l)).nil?
+        if l.start_with?('///') && !(m = %r!^///\s*<reference\s+path=(?:"([^"]+)"|'([^']+)')\s*/>\s*!.match(l)).nil?
           matched_path = m.captures.compact[0]
           l = l.sub(matched_path, File.join(escaped_dir, matched_path))
         end
@@ -35,7 +35,7 @@ def get_all_reference_paths(path, source, visited_paths=Set.new, &block)
       visited_paths << path
       source ||= File.read(path)
       source.each_line do |l|
-        if l.starts_with?('///') && !(m = %r!^///\s*<reference\s+path=(?:"([^"]+)"|'([^']+)')\s*/>\s*!.match(l)).nil?
+        if l.start_with?('///') && !(m = %r!^///\s*<reference\s+path=(?:"([^"]+)"|'([^']+)')\s*/>\s*!.match(l)).nil?
           matched_path = m.captures.compact[0]
           abs_matched_path = File.expand_path(matched_path, File.dirname(path))
           unless visited_paths.include? abs_matched_path
diff --git a/test/assets_test.rb b/test/assets_test.rb
index 23b28b6..e551230 100644
--- a/test/assets_test.rb
+++ b/test/assets_test.rb
@@ -35,12 +35,13 @@ def assets
     @app.assets
   end
 
-  test 'typescript.js is included in Sprockets environment' do
-    assert { assets["typescript"].filename.to_s.end_with?('/lib/assets/javascripts/typescript.js.erb') }
-    assert { assets["typescript"].source.include?('var ts;') }
-  end
+  # Run all tests in one block to avoid error from calling @app.initialize! multiple times
+  test 'generates assets successfully' do
+    # typescript.js is included in Sprockets environment
+    assert { assets['typescript'].filename.to_s.end_with?('/lib/assets/javascripts/typescript.js.erb') }
+    assert { assets['typescript'].source.include?('var ts;') }
 
-  test 'assets .js.ts is compiled from TypeScript to JavaScript' do
+    # 'assets .js.ts is compiled from TypeScript to JavaScript'
     assert { assets['javascripts/hello.js'].present? }
     assert { assets['javascripts/hello.js'].source.include?('var log_to_console = function (x) {') }
     assert { assets['javascripts/hello.js'].source.include?('var s = "Hello, world!";') }
diff --git a/test/template_handler_test.rb b/test/template_handler_test.rb
index b0aef0f..6b9d7f4 100644
--- a/test/template_handler_test.rb
+++ b/test/template_handler_test.rb
@@ -31,25 +31,25 @@ def source
 
   test 'typescript views are served as javascript' do
     get '/site/index.js'
-    assert_match /var x = 5;\s*/,
+    assert_match (/var x = 5;\s*/),
         source
   end
 
   test '<reference> to other .ts file works' do
     get '/site/ref1_2.js'
-    assert_match /var f = function \(x, y\) \{\s*return x \+ y;\s*\};\s*f\(1, 2\);\s*/,
+    assert_match (/var f = function \(x, y\) \{\s*return x \+ y;\s*\};\s*f\(1, 2\);\s*/),
         source
   end
 
   test '<reference> to other .d.ts file works' do
     get '/site/ref2_2.js'
-    assert_match /f\(1, 2\);\s*/,
+    assert_match (/f\(1, 2\);\s*/),
         source
   end
 
   test '<reference> to multiple .ts files works' do
     get '/site/ref3_1.js'
-    assert_match /var f1 = function \(\) \{\s*\};\s*var f2 = function \(\) \{\s*\};\s*f1\(\);\s*f2\(\);/,
+    assert_match (/var f1 = function \(\) \{\s*\};\s*var f2 = function \(\) \{\s*\};\s*f1\(\);\s*f2\(\);/),
         source
   end
 
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 7306cb5..c9905e9 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -3,10 +3,10 @@
 require 'coveralls'
 require 'simplecov'
 
-SimpleCov.formatter = SimpleCov::Formatter::MultiFormatter[
+SimpleCov.formatter = SimpleCov::Formatter::MultiFormatter.new([
     SimpleCov::Formatter::HTMLFormatter,
     Coveralls::SimpleCov::Formatter
-]
+])
 SimpleCov.start do
   add_filter '.bundle/'
 end
@@ -27,4 +27,4 @@ def copy_routes
 
   FileUtils.mkdir_p(destination)
   FileUtils.cp routes, destination
-end
\ No newline at end of file
+end