Send multipart email notification

src/Illuminate/Notifications/Messages/MailMessage.php

@@ -9,7 +9,10 @@ class MailMessage extends SimpleMessage
      *
      * @var string
      */
-    public $view = 'notifications::email';
+    public $view = [
+        'notifications::email.html',
+        'notifications::email.text',
+    ];
 
     /**
      * The view data for the message.

src/Illuminate/Notifications/resources/views/email-plain.blade.php

@@ -0,0 +1,19 @@
+{{ $level == 'error' ? 'Whoops!' : 'Hello!' }}
+
+<?php
+
+if (! empty($introLines)) {
+    echo implode("\r\n", $introLines), "\r\n\r\n";
+}
+
+if (isset($actionText)) {
+    echo "{$actionText}: {$actionUrl}\r\n\r\n";
+}
+
+if (! empty($outroLines)) {
+    echo implode("\r\n", $outroLines), "\r\n\r\n";
+}
+
+?>
+Regards,
+{{ config('app.name') }}

tests/Notifications/NotificationMailChannelTest.php

@@ -22,7 +22,9 @@ public function testMailIsSentByChannel()
             $mailer = Mockery::mock(Illuminate\Contracts\Mail\Mailer::class)
         );
 
-        $mailer->shouldReceive('send')->with('notifications::email', $data, Mockery::type('Closure'));
+        $view = ['notifications::email', 'notifications::email-plain'];
+
+        $mailer->shouldReceive('send')->with($view, $data, Mockery::type('Closure'));
 
         $channel->send($notifiable, $notification);
     }