From 5a0e0e72995472e315738dcea5b5a12d6e3d3489 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Tue, 3 Nov 2015 17:42:52 -0800
Subject: [PATCH] don't start a new process for every test file

we can just reuse the parent process.  We should figure out what files
are commonly required among the test files and try to require them in
the parent so that the require time cost is amortized across the
processes.
---
 railties/Rakefile | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/railties/Rakefile b/railties/Rakefile
index cf130a5f14..73d881b318 100644
--- a/railties/Rakefile
+++ b/railties/Rakefile
@@ -5,20 +5,33 @@ 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")
-      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
+      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 }
     end
   end
 end