Merge branch '6.4' into 7.0

* 6.4:
  [DI] Add note about testing service locators
  tip to not follow redirects when testing mailer

Author: javiereguiluz

mailer.rst

@@ -1807,6 +1807,13 @@ the :class:`Symfony\\Bundle\\FrameworkBundle\\Test\\MailerAssertionsTrait`::
         }
     }
 
+.. tip::
+
+   If your controller returns a redirect response after sending the email, make
+   sure to have your client *not* follow redirects. The kernel is rebooted after
+   following the redirection and the message will be lost from the mailer event
+   handler.
+
 .. _`Amazon SES`: https://github.com/symfony/symfony/blob/{version}/src/Symfony/Component/Mailer/Bridge/Amazon/README.md
 .. _`App Password`: https://support.google.com/accounts/answer/185833
 .. _`Brevo`: https://github.com/symfony/symfony/blob/{version}/src/Symfony/Component/Mailer/Bridge/Brevo/README.md

service_container/service_subscribers_locators.rst

@@ -1004,6 +1004,15 @@ To unit test a service subscriber, you can create a fake container::
     $serviceSubscriber = new MyService($container);
     // ...
 
+.. note::
+
+    When defining the service locator like this, beware that the
+    :method:`Symfony\\Contracts\\Service\\ServiceLocatorTrait::getProvidedServices`
+    of your container will use the return type of the closures as the values of the
+    returned array. If no return type is defined, the value will be ``?``. If you
+    want the values to reflect the classes of your services, the return type has
+    to be set on your closures.
+
 Another alternative is to mock it using ``PHPUnit``::
 
     use Psr\Container\ContainerInterface;