Revert "don't start a new process for every test file"

This reverts commit 5a0e0e72.

This commit causes railties tests on TravisCI to always return a 0 status (all tests passing), even when tests are failing. Reverting for now until a new solution can be found.

railties/Rakefile

@@ -5,33 +5,20 @@ task :default => :test
 desc "Run all unit tests"
 task :test => 'test:isolated'
 
-dash_i = [
-  'test',
-  'lib',
-  "#{File.dirname(__FILE__)}/../activesupport/lib",
-  "#{File.dirname(__FILE__)}/../actionpack/lib",
-  "#{File.dirname(__FILE__)}/../activemodel/lib"
-]
-
-dash_i.reverse_each do |x|
-  $:.unshift x unless $:.include? x
-end
-$-w = true
-
-require 'bundler/setup' unless defined?(Bundler)
-require 'active_support'
-
 namespace :test do
   task :isolated do
     dirs = (ENV["TEST_DIR"] || ENV["TEST_DIRS"] || "**").split(",")
     test_files = dirs.map { |dir| "test/#{dir}/*_test.rb" }
     Dir[*test_files].each do |file|
       next true if file.include?("fixtures")
-      puts "#{FileUtils::RUBY} -w -I#{dash_i.join ':'} #{file}"
-
-      # We could run these in parallel, but pretty much all of the
-      # railties tests already run in parallel, so ¯\_(⊙︿⊙)_/¯
-      Process.waitpid fork { ARGV.clear; load file }
+      dash_i = [
+        'test',
+        'lib',
+        "#{File.dirname(__FILE__)}/../activesupport/lib",
+        "#{File.dirname(__FILE__)}/../actionpack/lib",
+        "#{File.dirname(__FILE__)}/../activemodel/lib"
+      ]
+      ruby "-w", "-I#{dash_i.join ':'}", file
     end
   end
 end