Seperate test

test/setup_bundler_test.rb

@@ -483,6 +483,37 @@ def test_ensures_lockfile_remotes_are_relative_to_default_gemfile
   end
 
   def test_ruby_lsp_rails_is_automatically_included_in_rails_apps
+    Dir.mktmpdir do |dir|
+      FileUtils.mkdir("#{dir}/config")
+      FileUtils.cp("test/fixtures/rails_application.rb", "#{dir}/config/application.rb")
+      Dir.chdir(dir) do
+        File.write(File.join(dir, "Gemfile"), <<~GEMFILE)
+          source "https://rubygems.org"
+          gem "rails"
+        GEMFILE
+
+        capture_subprocess_io do
+          Bundler.with_unbundled_env do
+            # Run bundle install to generate the lockfile
+            system("bundle install")
+          end
+        end
+
+        Object.any_instance.expects(:system).with(
+          bundle_env(".ruby-lsp/Gemfile"),
+          "(bundle check || bundle install) 1>&2",
+        ).returns(true)
+        Bundler.with_unbundled_env do
+          run_script
+        end
+
+        assert_path_exists(".ruby-lsp/Gemfile")
+        assert_match('gem "ruby-lsp-rails"', File.read(".ruby-lsp/Gemfile"))
+      end
+    end
+  end
+
+  def test_ruby_lsp_rails_detection_handles_lang_from_environment
     original_encoding = Encoding.default_external
     Encoding.default_external = "us-ascii"