src/TestSessionEnvironment.php

@@ -21,7 +21,6 @@ use SilverStripe\ORM\DatabaseAdmin;
 use SilverStripe\ORM\DB;
 use SilverStripe\ORM\FieldType\DBDatetime;
 use SilverStripe\Versioned\Versioned;
-use Symfony\Component\Mailer\MailerInterface;
 use stdClass;
 
 /**
@@ -321,13 +320,15 @@ class TestSessionEnvironment
         }
 
         // Mailer
-        $mailer = $state->mailer ?? null;
-        if ($mailer && !is_a($mailer, MailerInterface::class, true)) {
-            throw new InvalidArgumentException(sprintf(
-                'Class "%s" does not implement %s',
-                $mailer,
-                MailerInterface::class
-            ));
+        $mailer = (isset($state->mailer)) ? $state->mailer : null;
+
+        if ($mailer) {
+            if (!class_exists($mailer ?? '') || !is_subclass_of($mailer, 'SilverStripe\\Control\\Email\\Mailer')) {
+                throw new InvalidArgumentException(sprintf(
+                    'Class "%s" is not a valid class, or subclass of Mailer',
+                    $mailer
+                ));
+            }
         }
 
         // Date and time

src/TestSessionHTTPMiddleware.php

@@ -4,14 +4,12 @@ namespace SilverStripe\TestSession;
 
 use SilverStripe\Control\Director;
 use SilverStripe\Control\Email\Email;
+use SilverStripe\Control\Email\Mailer;
 use SilverStripe\Control\HTTPRequest;
 use SilverStripe\Control\Middleware\HTTPMiddleware;
 use SilverStripe\Core\Injector\Injector;
 use SilverStripe\ORM\DB;
 use SilverStripe\ORM\FieldType\DBDatetime;
-use Symfony\Component\EventDispatcher\EventDispatcherInterface;
-use Symfony\Component\Mailer\MailerInterface;
-use Symfony\Component\Mailer\Transport\NullTransport;
 
 /**
  * Sets state previously initialized through {@link TestSessionController}.
@@ -69,12 +67,7 @@ class TestSessionHTTPMiddleware implements HTTPMiddleware
         // Register mailer
         if (isset($testState->mailer)) {
             $mailer = $testState->mailer;
-            $dispatcher = Injector::inst()->get(EventDispatcherInterface::class . '.mailer');
-            $transport = new NullTransport($dispatcher);
-            Injector::inst()->registerService(
-                new $mailer($transport, $dispatcher),
-                MailerInterface::class
-            );
+            Injector::inst()->registerService(new $mailer(), Mailer::class);
             Email::config()->set("send_all_emails_to", null);
             Email::config()->update('admin_email', 'no-reply@example.com');
         }