2 files changed, 16 insertions, 7 deletions
diff --git a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
index c06cd525d7..47b4cf745c 100644
--- a/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/test/test_helper.rb.tt
@@ -5,9 +5,9 @@ require 'rails/test_help'
 class ActiveSupport::TestCase
   # Run tests in parallel with specified workers
 <% if defined?(JRUBY_VERSION) || Gem.win_platform? -%>
-  parallelize(workers: 2, with: :threads)
+  parallelize(workers: :number_of_processors, with: :threads)
 <%- else -%>
-  parallelize(workers: 2)
+  parallelize(workers: :number_of_processors)
 <% end -%>
 
 <% unless options[:skip_active_record] -%>
diff --git a/railties/test/application/test_runner_test.rb b/railties/test/application/test_runner_test.rb
index 140703e118..55cfda82ea 100644
--- a/railties/test/application/test_runner_test.rb
+++ b/railties/test/application/test_runner_test.rb
@@ -523,6 +523,8 @@ module ApplicationTests
     end
 
     def test_run_in_parallel_with_processes
+      substitute_arguments_of_parallelize_method("workers: 2, with: :processes")
+
       file_name = create_parallel_processes_test_file
 
       app_file "db/schema.rb", <<-RUBY
@@ -540,11 +542,7 @@ module ApplicationTests
     end
 
     def test_run_in_parallel_with_threads
-      app_path("/test/test_helper.rb") do |file_name|
-        file = File.read(file_name)
-        file.sub!(/parallelize\(([^\)]*)\)/, "parallelize(\\1, with: :threads)")
-        File.write(file_name, file)
-      end
+      substitute_arguments_of_parallelize_method("workers: 2, with: :threads")
 
       file_name = create_parallel_threads_test_file
 
@@ -563,6 +561,8 @@ module ApplicationTests
     end
 
     def test_run_in_parallel_with_unmarshable_exception
+      substitute_arguments_of_parallelize_method("workers: 2, with: :processes")
+
       file = app_file "test/fail_test.rb", <<-RUBY
         require "test_helper"
         class FailTest < ActiveSupport::TestCase
@@ -587,6 +587,7 @@ module ApplicationTests
     end
 
     def test_run_in_parallel_with_unknown_object
+      substitute_arguments_of_parallelize_method("workers: 2, with: :processes")
       create_scaffold
       app_file "config/environments/test.rb", <<-RUBY
         Rails.application.configure do
@@ -966,6 +967,14 @@ module ApplicationTests
         RUBY
       end
 
+      def substitute_arguments_of_parallelize_method(arguments)
+        app_path("test/test_helper.rb") do |file_name|
+          file = File.read(file_name)
+          file.sub!(/parallelize\(([^\)]*)\)/, "parallelize(#{arguments})")
+          File.write(file_name, file)
+        end
+      end
+
       def create_env_test
         app_file "test/unit/env_test.rb", <<-RUBY
           require 'test_helper'