Merge pull request #35434 from matthewd/faster-isolated-ar

Copy the forking isolated test runner from railties

activerecord/Rakefile

@@ -66,8 +66,38 @@ end
         adapter_short = adapter == "db2" ? adapter : adapter[/^[a-z0-9]+/]
         puts [adapter, adapter_short].inspect
 
+        dash_i = [
+          "test",
+          "lib",
+          "../activesupport/lib",
+          "../activemodel/lib"
+        ].map { |dir| File.expand_path(dir, __dir__) }
+
+        dash_i.reverse_each do |x|
+          $:.unshift(x) unless $:.include?(x)
+        end
+        $-w = true
+
+        require "bundler/setup" unless defined?(Bundler)
+
+        # Every test file loads "cases/helper" first, so doing it
+        # post-fork gains us nothing.
+
+        # We need to dance around minitest autorun, though.
+        require "minitest"
+        Minitest.instance_eval do
+          alias _original_autorun autorun
+          def autorun
+            # no-op
+          end
+          require "cases/helper"
+          alias autorun _original_autorun
+        end
+
         failing_files = []
 
+        test_options = ENV["TESTOPTS"].to_s.split(/[\s]+/)
+
         test_files = (Dir["test/cases/**/*_test.rb"].reject {
           |x| x.include?("/adapters/")
         } + Dir["test/cases/adapters/#{adapter_short}/**/*_test.rb"]).sort
@@ -81,8 +111,26 @@ end
 
         test_files.each do |file|
           puts "--- #{file}"
-          success = sh(Gem.ruby, "-w", "-Itest", file)
-          unless success
+          fake_command = Shellwords.join([
+            FileUtils::RUBY,
+            "-w",
+            *dash_i.map { |dir| "-I#{Pathname.new(dir).relative_path_from(Pathname.pwd)}" },
+            file,
+          ])
+          puts fake_command
+
+          # We could run these in parallel, but pretty much all of the
+          # railties tests already run in parallel, so ¯\_(⊙︿⊙)_/¯
+          Process.waitpid fork {
+            ARGV.clear.concat test_options
+            Rake.application = nil
+
+            Minitest.autorun
+
+            load file
+          }
+
+          unless $?.success?
             failing_files << file
             puts "^^^ +++"
           end

activerecord/test/cases/unconnected_test.rb

@@ -11,6 +11,12 @@ class TestUnconnectedAdapter < ActiveRecord::TestCase
   def setup
     @underlying = ActiveRecord::Base.connection
     @specification = ActiveRecord::Base.remove_connection
+
+    # Clear out connection info from other pids (like a fork parent) too
+    pool_map = ActiveRecord::Base.connection_handler.instance_variable_get(:@owner_to_pool)
+    (pool_map.keys - [Process.pid]).each do |other_pid|
+      pool_map.delete(other_pid)
+    end
   end
 
   teardown do