only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/system/tests/modules/tabledrag_test/src/Form/TableDragTestForm.php
@@ -0,0 +1,154 @@
+<?php
+
+namespace Drupal\tabledrag_test\Form;
+
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\State\StateInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides a form for draggable table testing.
+ */
+class TableDragTestForm extends FormBase {
+
+  /**
+   * The state service.
+   *
+   * @var \Drupal\Core\State\StateInterface
+   */
+  protected $state;
+
+  /**
+   * Constructs a TableDragTestForm object.
+   *
+   * @param \Drupal\Core\State\StateInterface $state
+   *   The state service.
+   */
+  public function __construct(StateInterface $state) {
+    $this->state = $state;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static($container->get('state'));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'tabledrag_test_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $form['table'] = [
+      '#type' => 'table',
+      '#header' => [
+        [
+          'data' => $this->t('Text'),
+          'colspan' => 4,
+        ],
+        $this->t('Weight'),
+      ],
+      '#tabledrag' => [
+        [
+          'action' => 'order',
+          'relationship' => 'sibling',
+          'group' => 'tabledrag-test-weight',
+        ],
+        [
+          'action' => 'match',
+          'relationship' => 'parent',
+          'group' => 'tabledrag-test-parent',
+          'subgroup' => 'tabledrag-test-parent',
+          'source' => 'tabledrag-test-id',
+          'hidden' => TRUE,
+          'limit' => 2,
+        ],
+        [
+          'action' => 'depth',
+          'relationship' => 'group',
+          'group' => 'tabledrag-test-depth',
+          'hidden' => TRUE,
+        ],
+      ],
+      '#attributes' => ['id' => 'tabledrag-test-table'],
+    ];
+
+    foreach ($this->state->get('tabledrag_test_table') as $id => $row) {
+      if (!is_array($row)) {
+        $row = [];
+      }
+
+      $row += [
+        'parent' => '',
+        'weight' => 0,
+        'depth' => 0,
+        'classes' => [],
+        'draggable' => TRUE,
+      ];
+
+      if (!empty($row['draggable'])) {
+        $row['classes'][] = 'draggable';
+      }
+
+      $form['table'][$id] = [
+        'title' => [
+          'indentation' => [
+            '#theme' => 'indentation',
+            '#size' => $row['depth'],
+          ],
+          '#plain_text' => "Row with id $id",
+        ],
+        'id' => [
+          '#type' => 'hidden',
+          '#value' => $id,
+          '#attributes' => ['class' => ['tabledrag-test-id']],
+        ],
+        'parent' => [
+          '#type' => 'hidden',
+          '#default_value' => $row['parent'],
+          '#parents' => ['table', $id, 'parent'],
+          '#attributes' => ['class' => ['tabledrag-test-parent']],
+        ],
+        'depth' => [
+          '#type' => 'hidden',
+          '#default_value' => $row['depth'],
+          '#attributes' => ['class' => ['tabledrag-test-depth']],
+        ],
+        'weight' => [
+          '#type' => 'weight',
+          '#default_value' => $row['weight'],
+          '#attributes' => ['class' => ['tabledrag-test-weight']],
+        ],
+        '#attributes' => ['class' => $row['classes']],
+      ];
+    }
+
+    $form['save'] = [
+      '#type' => 'submit',
+      '#value' => $this->t('Save'),
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $test_table = [];
+    foreach ($form_state->getValue('table') as $row) {
+      $test_table[$row['id']] = $row;
+    }
+
+    $this->state->set('tabledrag_test_table', $test_table);
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/system/tests/modules/tabledrag_test/tabledrag_test.info.yml
@@ -0,0 +1,6 @@
+type: module
+name: 'TableDrag test'
+description: 'Draggable table test module.'
+core: 8.x
+package: Testing
+version: VERSION
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/system/tests/modules/tabledrag_test/tabledrag_test.routing.yml
@@ -0,0 +1,7 @@
+tabledrag_test.test_form:
+  path: '/tabledrag_test'
+  defaults:
+    _form: '\Drupal\tabledrag_test\Form\TableDragTestForm'
+    _title: 'Draggable table test'
+  requirements:
+    _access: 'TRUE'
only in patch2:
unchanged:
--- /dev/null
+++ b/core/tests/Drupal/FunctionalJavascriptTests/TableDrag/TableDragTest.php
@@ -0,0 +1,343 @@
+<?php
+
+namespace Drupal\FunctionalJavascriptTests\TableDrag;
+
+use Behat\Mink\Element\NodeElement;
+use Behat\Mink\Exception\ElementNotFoundException;
+use Behat\Mink\Exception\ExpectationException;
+use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
+
+/**
+ * Tests draggable table.
+ *
+ * @group javascript
+ */
+class TableDragTest extends JavascriptTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['tabledrag_test'];
+
+  /**
+   * The state service.
+   *
+   * @var \Drupal\Core\State\StateInterface
+   */
+  protected $state;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->state = $this->container->get('state');
+  }
+
+  /**
+   * Tests accessibility through keyboard of the tabledrag functionality.
+   */
+  public function testKeyboardAccessibility() {
+    $this->state->set('tabledrag_test_table', array_flip(range(1, 5)));
+
+    $this->drupalGet('tabledrag_test');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 3, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 4, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Nest the row with id 2 as child of row 1.
+    $this->moveRowWithKeyboard($this->findRowById(2), 'right');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 3, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 4, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Nest the row with id 3 as child of row 1.
+    $this->moveRowWithKeyboard($this->findRowById(3), 'right');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 3, 'weight' => -9, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 4, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Nest the row with id 3 as child of row 2.
+    $this->moveRowWithKeyboard($this->findRowById(3), 'right');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 3, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 4, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Nesting should be allowed to maximum level 3.
+    $this->moveRowWithKeyboard($this->findRowById(4), 'right', 4);
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 3, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 4, 'weight' => -9, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Re-order children of row 1.
+    $this->moveRowWithKeyboard($this->findRowById(4), 'up');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 4, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 3, 'weight' => -9, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Move back the row 3 to the 1st level.
+    $this->moveRowWithKeyboard($this->findRowById(3), 'left');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 4, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 3, 'weight' => -9, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+    $this->moveRowWithKeyboard($this->findRowById(3), 'left');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => -10, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 4, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 3, 'weight' => -9, 'parent' => '', 'indentation' => 0, 'changed' => TRUE],
+      ['id' => 5, 'weight' => -8, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Move row 3 to the last position.
+    $this->moveRowWithKeyboard($this->findRowById(3), 'down');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => -10, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 4, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 5, 'weight' => -9, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 3, 'weight' => -8, 'parent' => '', 'indentation' => 0, 'changed' => TRUE],
+    ]);
+
+    // Nothing happens when trying to move the last row further down.
+    $this->moveRowWithKeyboard($this->findRowById(3), 'down');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => -10, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 4, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 5, 'weight' => -9, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 3, 'weight' => -8, 'parent' => '', 'indentation' => 0, 'changed' => TRUE],
+    ]);
+
+    // Nest row 3 under 5. The max depth allowed should be 1.
+    $this->moveRowWithKeyboard($this->findRowById(3), 'right', 3);
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => -10, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 4, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 5, 'weight' => -9, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 3, 'weight' => -10, 'parent' => 5, 'indentation' => 1, 'changed' => TRUE],
+    ]);
+
+    // The first row of the table cannot be nested.
+    $this->moveRowWithKeyboard($this->findRowById(1), 'right');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => -10, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => TRUE],
+      ['id' => 4, 'weight' => -10, 'parent' => 2, 'indentation' => 2, 'changed' => TRUE],
+      ['id' => 5, 'weight' => -9, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 3, 'weight' => -10, 'parent' => 5, 'indentation' => 1, 'changed' => TRUE],
+    ]);
+  }
+
+  /**
+   * Tests the root and leaf behaviors for rows.
+   */
+  public function testRootLeafDraggableRowsWithKeyboard() {
+    $this->state->set('tabledrag_test_table', [
+      1 => [],
+      2 => ['parent' => 1, 'depth' => 1, 'classes' => ['tabledrag-leaf']],
+      3 => ['parent' => 1, 'depth' => 1],
+      4 => [],
+      5 => ['classes' => ['tabledrag-root']],
+    ]);
+
+    $this->drupalGet('tabledrag_test');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => 0, 'parent' => 1, 'indentation' => 1, 'changed' => FALSE],
+      ['id' => 3, 'weight' => 0, 'parent' => 1, 'indentation' => 1, 'changed' => FALSE],
+      ['id' => 4, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Rows marked as root cannot be moved as children of another row.
+    $this->moveRowWithKeyboard($this->findRowById(5), 'right');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => 0, 'parent' => 1, 'indentation' => 1, 'changed' => FALSE],
+      ['id' => 3, 'weight' => 0, 'parent' => 1, 'indentation' => 1, 'changed' => FALSE],
+      ['id' => 4, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Rows marked as leaf cannot have children. Trying to move the row #3
+    // as child of #2 should have no results.
+    $this->moveRowWithKeyboard($this->findRowById(3), 'right');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 2, 'weight' => 0, 'parent' => 1, 'indentation' => 1, 'changed' => FALSE],
+      ['id' => 3, 'weight' => 0, 'parent' => 1, 'indentation' => 1, 'changed' => FALSE],
+      ['id' => 4, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 5, 'weight' => 0, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Leaf can be still swapped and moved to first level.
+    $this->moveRowWithKeyboard($this->findRowById(2), 'down');
+    $this->moveRowWithKeyboard($this->findRowById(2), 'left');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => -10, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 3, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -9, 'parent' => '', 'indentation' => 0, 'changed' => TRUE  ],
+      ['id' => 4, 'weight' => -8, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 5, 'weight' => -7, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+    ]);
+
+    // Root rows can have children.
+    $this->moveRowWithKeyboard($this->findRowById(4), 'down');
+    $this->moveRowWithKeyboard($this->findRowById(4), 'right');
+    $this->assertDraggableTable([
+      ['id' => 1, 'weight' => -10, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 3, 'weight' => -10, 'parent' => 1, 'indentation' => 1, 'changed' => FALSE],
+      ['id' => 2, 'weight' => -9, 'parent' => '', 'indentation' => 0, 'changed' => TRUE],
+      ['id' => 5, 'weight' => -8, 'parent' => '', 'indentation' => 0, 'changed' => FALSE],
+      ['id' => 4, 'weight' => -10, 'parent' => 5, 'indentation' => 1, 'changed' => TRUE],
+    ]);
+  }
+
+  /**
+   * Asserts the whole structure of the draggable test table.
+   *
+   * @param array $structure
+   *   The table structure. Each entry represents a row and consists of:
+   *   - id: the expected value for the ID hidden field.
+   *   - weight: the expected row weight.
+   *   - parent: the expected parent ID for the row.
+   *   - indentation: how many indents the row should have.
+   *   - changed: whether or not the row should have been marked as changed.
+   */
+  protected function assertDraggableTable(array $structure) {
+    $rows = $this->getSession()->getPage()->findAll('xpath', '//table[@id="tabledrag-test-table"]/tbody/tr');
+    $this->assertSameSize($structure, $rows);
+
+    foreach ($structure as $delta => $expected) {
+      $this->assertTableRow($rows[$delta], $expected['id'], $expected['weight'], $expected['parent'], $expected['indentation'], $expected['changed']);
+    }
+  }
+
+  /**
+   * Asserts the values of a draggable row.
+   *
+   * @param \Behat\Mink\Element\NodeElement $row
+   *   The row element to assert.
+   * @param string $id
+   *   The expected value for the ID hidden input of the row.
+   * @param int $weight
+   *   The expected weight of the row.
+   * @param string $parent
+   *   The expected parent ID.
+   * @param int $indentation
+   *   The expected indentation of the row.
+   * @param bool $changed
+   *   Whether or not the row should have been marked as changed.
+   */
+  protected function assertTableRow(NodeElement $row, $id, $weight, $parent = '', $indentation = 0, $changed = FALSE) {
+    $this->assertEquals($id, $row->find('hidden_field_selector', ['hidden_field', "table[$id][id]"])->getValue());
+    $this->assertEquals($parent, $row->find('hidden_field_selector', ['hidden_field', "table[$id][parent]"])->getValue());
+    $this->assertEquals($weight, $row->findField("table[$id][weight]")->getValue());
+    $this->assertCount($indentation, $row->findAll('css', '.js-indentation.indentation'));
+    // A row is marked as changed when the related markup is present.
+    $this->assertEquals($changed, !empty($row->find('css', 'abbr.tabledrag-changed')));
+  }
+
+  /**
+   * Finds a row in the test table by the row ID.
+   *
+   * @param string $id
+   *   The ID of the row.
+   *
+   * @return \Behat\Mink\Element\NodeElement|mixed|null
+   *   The row element.
+   *
+   * @throws \Behat\Mink\Exception\ElementNotFoundException
+   *   Thrown when the row is not found.
+   */
+  protected function findRowById($id) {
+    $xpath = "//table[@id='tabledrag-test-table']/tbody/tr[.//input[@name='table[$id][id]']]";
+    $row = $this->getSession()->getPage()->find('xpath', $xpath);
+
+    if (!$row) {
+      throw new ElementNotFoundException($this->getSession(), 'row');
+    }
+
+    return $row;
+  }
+
+  /**
+   * Moves a row through the keyboard.
+   *
+   * @param \Behat\Mink\Element\NodeElement $row
+   *   The row to move.
+   * @param string $arrow
+   *   The arrow button to use to move the row. Either one of 'left', 'right',
+   *   'up' or 'down'.
+   * @param int $repeat
+   *   How many times to press the arrow button specified.
+   */
+  protected function moveRowWithKeyboard(NodeElement $row, $arrow, $repeat = 1) {
+    // Convert the arrow name to the browser key event code.
+    switch ($arrow) {
+      case 'left':
+        $key = 37;
+        break;
+
+      case 'right':
+        $key = 39;
+        break;
+
+      case 'up':
+        $key = 38;
+        break;
+
+      case 'down':
+        $key = 40;
+    }
+
+    if (is_null($key)) {
+      throw new \InvalidArgumentException('The direction parameter must be one of "left", "right", "up" or "down".');
+    }
+
+    $handle = $row->find('xpath', '//a[@class="tabledrag-handle"]');
+    $handle->focus();
+
+    for ($i = 0; $i < $repeat; $i++) {
+      $handle->keyDown($key);
+      $handle->keyUp($key);
+    }
+
+    $handle->blur();
+
+    // Give some time for the DOM manipulation.
+    $this->getSession()->wait(500);
+  }
+
+}