.../FunctionalJavascript/BigPipeRegressionTest.php | 56 +++++++++++++++++++---
 .../Functional/Render/PlaceholderMessageTest.php   |  8 ++--
 2 files changed, 54 insertions(+), 10 deletions(-)

diff --git a/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php b/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
index ab28073..addda90 100644
--- a/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
+++ b/core/modules/big_pipe/tests/src/FunctionalJavascript/BigPipeRegressionTest.php
@@ -6,6 +6,7 @@
 use Drupal\comment\Entity\Comment;
 use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
 use Drupal\comment\Tests\CommentTestTrait;
+use Drupal\Core\Url;
 use Drupal\editor\Entity\Editor;
 use Drupal\filter\Entity\FilterFormat;
 use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
@@ -27,13 +28,7 @@ class BigPipeRegressionTest extends JavascriptTestBase {
    * {@inheritdoc}
    */
   public static $modules = [
-    'node',
-    'comment',
     'big_pipe',
-    'history',
-    'editor',
-    'ckeditor',
-    'filter',
   ];
 
   /**
@@ -53,6 +48,14 @@ public function setUp() {
    * @see https://www.drupal.org/node/2698811
    */
   public function testCommentForm_2698811() {
+    $this->assertTrue($this->container->get('module_installer')->install([    'node',
+      'comment',
+      'history',
+      'editor',
+      'ckeditor',
+      'filter',
+    ], TRUE), 'Installed modules.');
+
     // Ensure an `article` node type exists.
     $this->createContentType(['type' => 'article']);
     $this->addDefaultCommentField('node', 'article');
@@ -114,4 +117,45 @@ public function testCommentForm_2698811() {
     $this->assertJsCondition($javascript);
   }
 
+  /**
+   * Ensure BigPipe renders the "messages" placeholder last.
+   *
+   * @see https://www.drupal.org/node/2712935
+   */
+  public function testMessages_2712935() {
+    $this->assertTrue($this->container->get('module_installer')->install(['render_placeholder_message_test'], TRUE), 'Installed modules.');
+
+    $this->drupalLogin($this->drupalCreateUser());
+    $messages_markup = '<div role="contentinfo" aria-label="Status message"';
+
+    $test_routes = [
+      // Messages placeholder rendered first.
+      'render_placeholder_message_test.first',
+      // Messages placeholder rendered after one, before another.
+      'render_placeholder_message_test.middle',
+      // Messages placeholder rendered last.
+      'render_placeholder_message_test.last',
+    ];
+
+    $assert = $this->assertSession();
+    foreach ($test_routes as $route) {
+      // Verify that we start off with zero messages queued.
+      $this->drupalGet(Url::fromRoute('render_placeholder_message_test.queued'));
+      $assert->responseNotContains($messages_markup);
+
+      // Verify the test case at this route behaves as expected.
+      $this->drupalGet(Url::fromRoute($route));
+      $assert->elementContains('css', 'p.logged-message:nth-of-type(1)', 'Message: P1');
+      $assert->elementContains('css', 'p.logged-message:nth-of-type(2)', 'Message: P2');
+      $assert->responseContains($messages_markup);
+      $assert->elementExists('css', 'div[aria-label="Status message"] ul');
+      $assert->elementContains('css', 'div[aria-label="Status message"] ul li:nth-of-type(1)', 'P1');
+      $assert->elementContains('css', 'div[aria-label="Status message"] ul li:nth-of-type(2)', 'P2');
+
+      // Verify that we end with all messages printed, hence again zero queued.
+      $this->drupalGet(Url::fromRoute('render_placeholder_message_test.queued'));
+      $assert->responseNotContains($messages_markup);
+    }
+  }
+
 }
diff --git a/core/modules/system/tests/src/Functional/Render/PlaceholderMessageTest.php b/core/modules/system/tests/src/Functional/Render/PlaceholderMessageTest.php
index 8ededd1..185ca49 100644
--- a/core/modules/system/tests/src/Functional/Render/PlaceholderMessageTest.php
+++ b/core/modules/system/tests/src/Functional/Render/PlaceholderMessageTest.php
@@ -23,7 +23,7 @@ class PlaceholderMessageTest extends BrowserTestBase {
    * Test rendering of message placeholder.
    */
   public function testMessagePlaceholder() {
-    $messages_markup = '<div role="contentinfo" aria-label="Status message" class="messages';
+    $messages_markup = '<div role="contentinfo" aria-label="Status message"';
 
     $test_routes = [
       // Messages placeholder rendered first.
@@ -45,9 +45,9 @@ public function testMessagePlaceholder() {
       $assert->elementContains('css', 'p.logged-message:nth-of-type(1)', 'Message: P1');
       $assert->elementContains('css', 'p.logged-message:nth-of-type(2)', 'Message: P2');
       $assert->responseContains($messages_markup);
-      $assert->elementExists('css', 'div.messages .messages__list');
-      $assert->elementContains('css', 'div.messages .messages__list .messages__item:nth-of-type(1)', 'P1');
-      $assert->elementContains('css', 'div.messages .messages__list .messages__item:nth-of-type(2)', 'P2');
+      $assert->elementExists('css', 'div[aria-label="Status message"] ul');
+      $assert->elementContains('css', 'div[aria-label="Status message"] ul li:nth-of-type(1)', 'P1');
+      $assert->elementContains('css', 'div[aria-label="Status message"] ul li:nth-of-type(2)', 'P2');
 
       // Verify that we end with all messages printed, hence again zero queued.
       $this->drupalGet(Url::fromRoute('render_placeholder_message_test.queued'));