2 files changed, 41 insertions, 2 deletions
diff --git a/activerecord/lib/active_record/fixtures.rb b/activerecord/lib/active_record/fixtures.rb
index d9a75d9ad6..8f022ff7a7 100644
--- a/activerecord/lib/active_record/fixtures.rb
+++ b/activerecord/lib/active_record/fixtures.rb
@@ -874,6 +874,7 @@ module ActiveRecord
       class_attribute :use_instantiated_fixtures, default: false # true, false, or :no_instances
       class_attribute :pre_loaded_fixtures, default: false
       class_attribute :config, default: ActiveRecord::Base
+      class_attribute :lock_threads, default: true
     end
 
     module ClassMethods
@@ -973,7 +974,7 @@ module ActiveRecord
         @fixture_connections = enlist_fixture_connections
         @fixture_connections.each do |connection|
           connection.begin_transaction joinable: false
-          connection.pool.lock_thread = true
+          connection.pool.lock_thread = true if lock_threads
         end
 
         # When connections are established in the future, begin a transaction too
@@ -989,7 +990,7 @@ module ActiveRecord
 
             if connection && !@fixture_connections.include?(connection)
               connection.begin_transaction joinable: false
-              connection.pool.lock_thread = true
+              connection.pool.lock_thread = true if lock_threads
               @fixture_connections << connection
             end
           end
diff --git a/activerecord/lib/active_record/test_databases.rb b/activerecord/lib/active_record/test_databases.rb
new file mode 100644
index 0000000000..606a3b0fb5
--- /dev/null
+++ b/activerecord/lib/active_record/test_databases.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require "active_support/testing/parallelization"
+
+module ActiveRecord
+  module TestDatabases # :nodoc:
+    ActiveSupport::Testing::Parallelization.after_fork_hook do |i|
+      create_and_migrate(i, spec_name: Rails.env)
+    end
+
+    ActiveSupport::Testing::Parallelization.run_cleanup_hook do |i|
+      drop(i, spec_name: Rails.env)
+    end
+
+    def self.create_and_migrate(i, spec_name:)
+      old, ENV["VERBOSE"] = ENV["VERBOSE"], "false"
+
+      connection_spec = ActiveRecord::Base.configurations[spec_name]
+
+      connection_spec["database"] += "-#{i}"
+      ActiveRecord::Tasks::DatabaseTasks.create(connection_spec)
+      ActiveRecord::Base.establish_connection(connection_spec)
+      ActiveRecord::Tasks::DatabaseTasks.migrate
+    ensure
+      ActiveRecord::Base.establish_connection(ActiveRecord::Base.configurations[Rails.env])
+      ENV["VERBOSE"] = old
+    end
+
+    def self.drop(i, spec_name:)
+      old, ENV["VERBOSE"] = ENV["VERBOSE"], "false"
+      connection_spec = ActiveRecord::Base.configurations[spec_name]
+
+      ActiveRecord::Tasks::DatabaseTasks.drop(connection_spec)
+    ensure
+      ENV["VERBOSE"] = old
+    end
+  end
+end