Closes rails/rails#18864: Renaming transactional fixtures to transactional tests

I’m renaming all instances of `use_transcational_fixtures` to
`use_transactional_tests` and “transactional fixtures” to
“transactional tests”.

I’m deprecating `use_transactional_fixtures=`. So anyone who is
explicitly setting this will get a warning telling them to use
`use_transactional_tests=` instead.

I’m maintaining backwards compatibility—both forms will work.
`use_transactional_tests` will check to see if
`use_transactional_fixtures` is set and use that, otherwise it will use
itself. But because `use_transactional_tests` is a class attribute
(created with `class_attribute`) this requires a little bit of hoop
jumping. The writer method that `class_attribute` generates defines a
new reader method that return the value being set. Which means we can’t
set the default of `true` using `use_transactional_tests=` as was done
previously because that won’t take into account anyone using
`use_transactional_fixtures`. Instead I defined the reader method
manually and it checks `use_transactional_fixtures`. If it was set then
it should be used, otherwise it should return the default, which is
`true`. If someone uses `use_transactional_tests=` then it will
overwrite the backwards-compatible method with whatever they set.

1 files changed, 3 insertions, 3 deletions

diff --git a/activerecord/test/cases/defaults_test.rb b/activerecord/test/cases/defaults_test.rb
index b9db0d0123..67fddebf45 100644
--- a/activerecord/test/cases/defaults_test.rb
+++ b/activerecord/test/cases/defaults_test.rb
@@ -90,14 +90,14 @@ end
 if current_adapter?(:MysqlAdapter, :Mysql2Adapter)
   class DefaultsTestWithoutTransactionalFixtures < ActiveRecord::TestCase
     # ActiveRecord::Base#create! (and #save and other related methods) will
-    # open a new transaction. When in transactional fixtures mode, this will
+    # open a new transaction. When in transactional tests mode, this will
     # cause Active Record to create a new savepoint. However, since MySQL doesn't
     # support DDL transactions, creating a table will result in any created
     # savepoints to be automatically released. This in turn causes the savepoint
     # release code in AbstractAdapter#transaction to fail.
     #
-    # We don't want that to happen, so we disable transactional fixtures here.
-    self.use_transactional_fixtures = false
+    # We don't want that to happen, so we disable transactional tests here.
+    self.use_transactional_tests = false
 
     def using_strict(strict)
       connection = ActiveRecord::Base.remove_connection