only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/block/tests/src/FunctionalJavascript/BlockScreenReaderFilterTest.php
@@ -0,0 +1,92 @@
+<?php
+
+namespace Drupal\Tests\system\FunctionalJavascript;
+
+use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
+
+/**
+ * Tests the JavaScript functionality of the block add filter.
+ *
+ * @group block
+ */
+class BlockScreenReaderFilterTest extends JavascriptTestBase {
+
+  public static $modules = array('block');
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $admin_user = $this->drupalCreateUser([
+      'administer blocks',
+    ]);
+    $this->drupalLogin($admin_user);
+  }
+
+  /**
+   * Tests block filtering screen reader updates.
+   */
+  public function testBlockFilter() {
+
+    // Find the module filter field.
+    $this->drupalGet('admin/structure/block');
+    $assertSession = $this->assertSession();
+    $assertSession->statusCodeEquals(200);
+    $session = $this->getSession();
+    $page = $session->getPage();
+
+    $page->find('css', '#edit-blocks-region-header-title')->click();
+
+    $assertSession->assertWaitOnAjaxRequest();
+
+    $filter = $page->find('css', '.block-filter-text');
+
+    // Get all block rows, for assertions later.
+    $block_rows = $page->findAll('css', '.block-add-table tbody tr');
+
+    // Test block filter reduces the number of visible rows.
+    $filter->setValue('ad');
+    $session->wait(1000, 'jQuery("#drupal-live-announce").html().indexOf("blocks are available") > -1');
+
+    $visible_rows = $this->filterVisibleElements($block_rows);
+    self::assertNotEquals(count($block_rows), count($visible_rows));
+
+    // Test Drupal.announce() message when multiple matches are expected.
+    $expected_message = count($visible_rows) . ' blocks are available in the modified list.';
+    $assertSession->elementTextContains('css', '#drupal-live-announce', $expected_message);
+
+    // Test Drupal.announce() message only one match is expected.
+    // Using a very specific block name, we expect only one row.
+    $filter->setValue('Drupal');
+    $session->wait(1000, 'jQuery("#drupal-live-announce").html().indexOf("block is available") > -1');
+    $visible_rows = $this->filterVisibleElements($block_rows);
+    self::assertEquals(1, count($visible_rows));
+    $expected_message = '1 block is available in the modified list.';
+    $assertSession->elementTextContains('css', '#drupal-live-announce', $expected_message);
+
+    // Test Drupal.announce() message when no matches are expected.
+    $filter->setValue('Pan-Galactic Gargle Blaster');
+    $session->wait(1000, 'jQuery("#drupal-live-announce").html().indexOf("0 blocks are available") > -1');
+    $visible_rows = $this->filterVisibleElements($block_rows);
+    self::assertEquals(0, count($visible_rows));
+
+    $expected_message = '0 blocks are available in the modified list.';
+    $assertSession->elementTextContains('css', '#drupal-live-announce', $expected_message);
+  }
+
+  /**
+   * Removes any non-visible elements from the passed array.
+   *
+   * @param array $elements
+   * @return array
+   */
+  protected function filterVisibleElements($elements) {
+    $elements = array_filter($elements, function($element) {
+      return $element->isVisible();
+    });
+    return $elements;
+  }
+
+}