Issue #3339659 by kunal.sachdev, tedbow, yash.rode: UpdateReady form does not have primary button

src/Form/UpdateReady.php

@@ -164,6 +164,7 @@ final class UpdateReady extends UpdateFormBase {
       '#type' => 'submit',
       '#value' => $this->t('Continue'),
     ];
+    $form['actions']['submit']['#button_type'] = 'primary';
     return $form;
   }
 

tests/src/Functional/AutomaticUpdatesFunctionalTestBase.php

@@ -136,6 +136,8 @@ abstract class AutomaticUpdatesFunctionalTestBase extends BrowserTestBase {
     $assert_session = $this->assertSession();
     $assert_session->addressMatches('/\/admin\/automatic-update-ready\/[a-zA-Z0-9_\-]+$/');
     $assert_session->pageTextContainsOnce('Drupal core will be updated to ' . $target_version);
+    $button = $assert_session->buttonExists("Continue");
+    $this->assertTrue($button->hasClass('button--primary'));
   }
 
   /**