1 files changed, 96 insertions, 11 deletions

diff --git a/activesupport/lib/active_support/test_case.rb b/activesupport/lib/active_support/test_case.rb
index bc42758f76..f17743b6db 100644
--- a/activesupport/lib/active_support/test_case.rb
+++ b/activesupport/lib/active_support/test_case.rb
@@ -2,16 +2,16 @@
 
 gem "minitest" # make sure we get the gem, not stdlib
 require "minitest"
-require_relative "testing/tagged_logging"
-require_relative "testing/setup_and_teardown"
-require_relative "testing/assertions"
-require_relative "testing/deprecation"
-require_relative "testing/declarative"
-require_relative "testing/isolation"
-require_relative "testing/constant_lookup"
-require_relative "testing/time_helpers"
-require_relative "testing/file_fixtures"
-require_relative "core_ext/kernel/reporting"
+require "active_support/testing/tagged_logging"
+require "active_support/testing/setup_and_teardown"
+require "active_support/testing/assertions"
+require "active_support/testing/deprecation"
+require "active_support/testing/declarative"
+require "active_support/testing/isolation"
+require "active_support/testing/constant_lookup"
+require "active_support/testing/time_helpers"
+require "active_support/testing/file_fixtures"
+require "active_support/testing/parallelization"
 
 module ActiveSupport
   class TestCase < ::Minitest::Test
@@ -40,12 +40,97 @@ module ActiveSupport
       def test_order
         ActiveSupport.test_order ||= :random
       end
+
+      # Parallelizes the test suite.
+      #
+      # Takes a +workers+ argument that controls how many times the process
+      # is forked. For each process a new database will be created suffixed
+      # with the worker number.
+      #
+      #   test-database-0
+      #   test-database-1
+      #
+      # If <tt>ENV["PARALLEL_WORKERS"]</tt> is set the workers argument will be ignored
+      # and the environment variable will be used instead. This is useful for CI
+      # environments, or other environments where you may need more workers than
+      # you do for local testing.
+      #
+      # If the number of workers is set to +1+ or fewer, the tests will not be
+      # parallelized.
+      #
+      # The default parallelization method is to fork processes. If you'd like to
+      # use threads instead you can pass <tt>with: :threads</tt> to the +parallelize+
+      # method. Note the threaded parallelization does not create multiple
+      # database and will not work with system tests at this time.
+      #
+      #   parallelize(workers: 2, with: :threads)
+      #
+      # The threaded parallelization uses Minitest's parallel executor directly.
+      # The processes parallelization uses a Ruby Drb server.
+      def parallelize(workers: 2, with: :processes)
+        workers = ENV["PARALLEL_WORKERS"].to_i if ENV["PARALLEL_WORKERS"]
+
+        return if workers <= 1
+
+        executor = case with
+                   when :processes
+                     Testing::Parallelization.new(workers)
+                   when :threads
+                     Minitest::Parallel::Executor.new(workers)
+                   else
+                     raise ArgumentError, "#{with} is not a supported parallelization executor."
+        end
+
+        self.lock_threads = false if defined?(self.lock_threads) && with == :threads
+
+        Minitest.parallel_executor = executor
+
+        parallelize_me!
+      end
+
+      # Set up hook for parallel testing. This can be used if you have multiple
+      # databases or any behavior that needs to be run after the process is forked
+      # but before the tests run.
+      #
+      # Note: this feature is not available with the threaded parallelization.
+      #
+      # In your +test_helper.rb+ add the following:
+      #
+      #   class ActiveSupport::TestCase
+      #     parallelize_setup do
+      #       # create databases
+      #     end
+      #   end
+      def parallelize_setup(&block)
+        ActiveSupport::Testing::Parallelization.after_fork_hook do |worker|
+          yield worker
+        end
+      end
+
+      # Clean up hook for parallel testing. This can be used to drop databases
+      # if your app uses multiple write/read databases or other clean up before
+      # the tests finish. This runs before the forked process is closed.
+      #
+      # Note: this feature is not available with the threaded parallelization.
+      #
+      # In your +test_helper.rb+ add the following:
+      #
+      #   class ActiveSupport::TestCase
+      #     parallelize_teardown do
+      #       # drop databases
+      #     end
+      #   end
+      def parallelize_teardown(&block)
+        ActiveSupport::Testing::Parallelization.run_cleanup_hook do |worker|
+          yield worker
+        end
+      end
     end
 
     alias_method :method_name, :name
 
     include ActiveSupport::Testing::TaggedLogging
-    include ActiveSupport::Testing::SetupAndTeardown
+    prepend ActiveSupport::Testing::SetupAndTeardown
     include ActiveSupport::Testing::Assertions
     include ActiveSupport::Testing::Deprecation
     include ActiveSupport::Testing::TimeHelpers