TableDragTest.php

<?php

declare (strict_types=1);
namespace Drupal\FunctionalJavascriptTests\TableDrag;

use Behat\Mink\Element\NodeElement;
use Behat\Mink\Exception\ExpectationException;
use Drupal\FunctionalJavascriptTests\WebDriverTestBase;

/**
 * Tests draggable table.
 *
 * @group javascript
 */
class TableDragTest extends WebDriverTestBase {
    
    /**
     * Class used to verify that dragging operations are in execution.
     */
    const DRAGGING_CSS_CLASS = 'tabledrag-test-dragging';
    
    /**
     * {@inheritdoc}
     */
    protected static $modules = [
        'tabledrag_test',
    ];
    
    /**
     * {@inheritdoc}
     */
    protected $defaultTheme = 'stark';
    
    /**
     * The state service.
     *
     * @var \Drupal\Core\State\StateInterface
     */
    protected $state;
    
    /**
     * Xpath selector for finding tabledrag indentation elements in a table row.
     *
     * @var string
     */
    protected static $indentationXpathSelector = 'child::td[1]/*[contains(concat(" ", normalize-space(@class), " "), " js-indentation ")][contains(concat(" ", normalize-space(@class), " "), " indentation ")]';
    
    /**
     * Xpath selector for finding the tabledrag changed marker.
     *
     * @var string
     */
    protected static $tabledragChangedXpathSelector = 'child::td[1]/abbr[contains(concat(" ", normalize-space(@class), " "), " tabledrag-changed ")]';
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        $this->state = $this->container
            ->get('state');
    }
    
    /**
     * Tests row weight switch.
     */
    public function testRowWeightSwitch() : void {
        $this->state
            ->set('tabledrag_test_table', array_flip(range(1, 3)));
        $this->drupalGet('tabledrag_test');
        $session = $this->getSession();
        $page = $session->getPage();
        $weight_select1 = $page->findField("table[1][weight]");
        $weight_select2 = $page->findField("table[2][weight]");
        $weight_select3 = $page->findField("table[3][weight]");
        // Check that rows weight selects are hidden.
        $this->assertFalse($weight_select1->isVisible());
        $this->assertFalse($weight_select2->isVisible());
        $this->assertFalse($weight_select3->isVisible());
        // Toggle row weight selects as visible.
        $this->findWeightsToggle('Show row weights')
            ->click();
        // Check that rows weight selects are visible.
        $this->assertTrue($weight_select1->isVisible());
        $this->assertTrue($weight_select2->isVisible());
        $this->assertTrue($weight_select3->isVisible());
        // Toggle row weight selects back to hidden.
        $this->findWeightsToggle('Hide row weights')
            ->click();
        // Check that rows weight selects are hidden again.
        $this->assertFalse($weight_select1->isVisible());
        $this->assertFalse($weight_select2->isVisible());
        $this->assertFalse($weight_select3->isVisible());
    }
    
    /**
     * Tests draggable table drag'n'drop.
     */
    public function testDragAndDrop() : void {
        $this->state
            ->set('tabledrag_test_table', array_flip(range(1, 3)));
        $this->drupalGet('tabledrag_test');
        $session = $this->getSession();
        $page = $session->getPage();
        // Confirm touchevents detection is loaded with Tabledrag
        $this->assertNotNull($this->assertSession()
            ->waitForElement('css', 'html.no-touchevents'));
        $weight_select1 = $page->findField("table[1][weight]");
        $weight_select2 = $page->findField("table[2][weight]");
        $weight_select3 = $page->findField("table[3][weight]");
        // Check that initially the rows are in the correct order.
        $this->assertOrder([
            'Row with id 1',
            'Row with id 2',
            'Row with id 3',
        ]);
        // Check that the 'unsaved changes' text is not present in the message area.
        $this->assertSession()
            ->pageTextNotContains('You have unsaved changes.');
        $row1 = $this->findRowById(1)
            ->find('css', 'a.tabledrag-handle');
        $row2 = $this->findRowById(2)
            ->find('css', 'a.tabledrag-handle');
        $row3 = $this->findRowById(3)
            ->find('css', 'a.tabledrag-handle');
        // Drag row1 over row2.
        $row1->dragTo($row2);
        // Check that the 'unsaved changes' text was added in the message area.
        $this->assertSession()
            ->waitForText('You have unsaved changes.');
        // Check that row1 and row2 were swapped.
        $this->assertOrder([
            'Row with id 2',
            'Row with id 1',
            'Row with id 3',
        ]);
        // Check that weights were changed.
        $this->assertGreaterThan($weight_select2->getValue(), $weight_select1->getValue());
        $this->assertGreaterThan($weight_select2->getValue(), $weight_select3->getValue());
        $this->assertGreaterThan($weight_select1->getValue(), $weight_select3->getValue());
        // Now move the last row (row3) in the second position. row1 should go last.
        $row3->dragTo($row1);
        // Check that the order is: row2, row3 and row1.
        $this->assertOrder([
            'Row with id 2',
            'Row with id 3',
            'Row with id 1',
        ]);
    }
    
    /**
     * Tests accessibility through keyboard of the tabledrag functionality.
     */
    public function testKeyboardAccessibility() : void {
        $this->assertKeyboardAccessibility();
    }
    
    /**
     * Asserts accessibility through keyboard of a test draggable table.
     *
     * @param string $drupal_path
     *   The drupal path where the '#tabledrag-test-table' test table is present.
     *   Defaults to 'tabledrag_test'.
     * @param array|null $structure
     *   The expected table structure. If this isn't specified or equals NULL,
     *   then the expected structure will be set by this method. Defaults to NULL.
     *
     * @internal
     */
    protected function assertKeyboardAccessibility(string $drupal_path = 'tabledrag_test', ?array $structure = NULL) : void {
        $expected_table = $structure ?: [
            [
                'id' => '1',
                'weight' => 0,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            [
                'id' => '2',
                'weight' => 0,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            [
                'id' => '3',
                'weight' => 0,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            [
                'id' => '4',
                'weight' => 0,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            [
                'id' => '5',
                'weight' => 0,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
        ];
        if (!empty($drupal_path)) {
            $this->state
                ->set('tabledrag_test_table', array_flip(range(1, 5)));
            $this->drupalGet($drupal_path);
        }
        $this->assertDraggableTable($expected_table);
        // Nest the row with id 2 as child of row 1.
        $this->moveRowWithKeyboard($this->findRowById(2), 'right');
        $expected_table[1] = [
            'id' => '2',
            'weight' => -10,
            'parent' => '1',
            'indentation' => 1,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
        // Nest the row with id 3 as child of row 1.
        $this->moveRowWithKeyboard($this->findRowById(3), 'right');
        $expected_table[2] = [
            'id' => '3',
            'weight' => -9,
            'parent' => '1',
            'indentation' => 1,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
        // Nest the row with id 3 as child of row 2.
        $this->moveRowWithKeyboard($this->findRowById(3), 'right');
        $expected_table[2] = [
            'id' => '3',
            'weight' => -10,
            'parent' => '2',
            'indentation' => 2,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
        // Nesting should be allowed to maximum level 2.
        $this->moveRowWithKeyboard($this->findRowById(4), 'right', 4);
        $expected_table[3] = [
            'id' => '4',
            'weight' => -9,
            'parent' => '2',
            'indentation' => 2,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
        // Re-order children of row 1.
        $this->moveRowWithKeyboard($this->findRowById(4), 'up');
        $expected_table[2] = [
            'id' => '4',
            'weight' => -10,
            'parent' => '2',
            'indentation' => 2,
            'changed' => TRUE,
        ];
        $expected_table[3] = [
            'id' => '3',
            'weight' => -9,
            'parent' => '2',
            'indentation' => 2,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
        // Move back the row 3 to the 1st level.
        $this->moveRowWithKeyboard($this->findRowById(3), 'left');
        $expected_table[3] = [
            'id' => '3',
            'weight' => -9,
            'parent' => '1',
            'indentation' => 1,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
        $this->moveRowWithKeyboard($this->findRowById(3), 'left');
        $expected_table[0] = [
            'id' => '1',
            'weight' => -10,
            'parent' => '',
            'indentation' => 0,
            'changed' => FALSE,
        ];
        $expected_table[3] = [
            'id' => '3',
            'weight' => -9,
            'parent' => '',
            'indentation' => 0,
            'changed' => TRUE,
        ];
        $expected_table[4] = [
            'id' => '5',
            'weight' => -8,
            'parent' => '',
            'indentation' => 0,
            'changed' => FALSE,
        ];
        $this->assertDraggableTable($expected_table);
        // Move row 3 to the last position.
        $this->moveRowWithKeyboard($this->findRowById(3), 'down');
        $expected_table[3] = [
            'id' => '5',
            'weight' => -9,
            'parent' => '',
            'indentation' => 0,
            'changed' => FALSE,
        ];
        $expected_table[4] = [
            'id' => '3',
            'weight' => -8,
            'parent' => '',
            'indentation' => 0,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
        // Nothing happens when trying to move the last row further down.
        $this->moveRowWithKeyboard($this->findRowById(3), 'down');
        $this->assertDraggableTable($expected_table);
        // Nest row 3 under 5. The max depth allowed should be 1.
        $this->moveRowWithKeyboard($this->findRowById(3), 'right', 3);
        $expected_table[4] = [
            'id' => '3',
            'weight' => -10,
            'parent' => '5',
            'indentation' => 1,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
        // The first row of the table cannot be nested.
        $this->moveRowWithKeyboard($this->findRowById(1), 'right');
        $this->assertDraggableTable($expected_table);
        // Move a row which has nested children. The children should move with it,
        // with nesting preserved. Swap the order of the top-level rows by moving
        // row 1 to after row 3.
        $this->moveRowWithKeyboard($this->findRowById(1), 'down', 2);
        $expected_table[0] = [
            'id' => '5',
            'weight' => -10,
            'parent' => '',
            'indentation' => 0,
            'changed' => FALSE,
        ];
        $expected_table[3] = $expected_table[1];
        $expected_table[1] = $expected_table[4];
        $expected_table[4] = $expected_table[2];
        $expected_table[2] = [
            'id' => '1',
            'weight' => -9,
            'parent' => '',
            'indentation' => 0,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
    }
    
    /**
     * Tests the root and leaf behaviors for rows.
     */
    public function testRootLeafDraggableRowsWithKeyboard() : void {
        $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');
        $expected_table = [
            [
                '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,
            ],
        ];
        $this->assertDraggableTable($expected_table);
        // Rows marked as root cannot be moved as children of another row.
        $this->moveRowWithKeyboard($this->findRowById(5), 'right');
        $this->assertDraggableTable($expected_table);
        // 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');
        $this->assertDraggableTable($expected_table);
        // Leaf can be still swapped and moved to first level.
        $this->moveRowWithKeyboard($this->findRowById(2), 'down');
        $this->moveRowWithKeyboard($this->findRowById(2), 'left');
        $expected_table[0]['weight'] = -10;
        $expected_table[1]['id'] = '3';
        $expected_table[1]['weight'] = -10;
        $expected_table[2] = [
            'id' => '2',
            'weight' => -9,
            'parent' => '',
            'indentation' => 0,
            'changed' => TRUE,
        ];
        $expected_table[3]['weight'] = -8;
        $expected_table[4]['weight'] = -7;
        $this->assertDraggableTable($expected_table);
        // Root rows can have children.
        $this->moveRowWithKeyboard($this->findRowById(4), 'down');
        $this->moveRowWithKeyboard($this->findRowById(4), 'right');
        $expected_table[3]['id'] = '5';
        $expected_table[4] = [
            'id' => '4',
            'weight' => -10,
            'parent' => '5',
            'indentation' => 1,
            'changed' => TRUE,
        ];
        $this->assertDraggableTable($expected_table);
    }
    
    /**
     * Tests the warning that appears upon making changes to a tabledrag table.
     */
    public function testTableDragChangedWarning() : void {
        $this->drupalGet('tabledrag_test');
        // By default no text is visible.
        $this->assertSession()
            ->pageTextNotContains('You have unsaved changes.');
        // Try to make a non-allowed action, like moving further down the last row.
        // No changes happen, so no message should be shown.
        $this->moveRowWithKeyboard($this->findRowById(5), 'down');
        $this->assertSession()
            ->pageTextNotContains('You have unsaved changes.');
        // Make a change. The message will appear.
        $this->moveRowWithKeyboard($this->findRowById(5), 'right');
        $this->assertSession()
            ->pageTextContainsOnce('You have unsaved changes.');
        // Make another change, the text will stay visible and appear only once.
        $this->moveRowWithKeyboard($this->findRowById(2), 'up');
        $this->assertSession()
            ->pageTextContainsOnce('You have unsaved changes.');
    }
    
    /**
     * Asserts that several pieces of markup are in a given order in the page.
     *
     * @param string[] $items
     *   An ordered list of strings.
     *
     * @throws \Behat\Mink\Exception\ExpectationException
     *   When any of the given string is not found.
     *
     * @todo Remove this and use the WebAssert method when #2817657 is done.
     *
     * @internal
     */
    protected function assertOrder(array $items) : void {
        $session = $this->getSession();
        $text = $session->getPage()
            ->getHtml();
        $strings = [];
        foreach ($items as $item) {
            if (($pos = strpos($text, $item)) === FALSE) {
                throw new ExpectationException("Cannot find '{$item}' in the page", $session->getDriver());
            }
            $strings[$pos] = $item;
        }
        ksort($strings);
        $this->assertSame($items, array_values($strings), "Strings found on the page but incorrectly ordered.");
    }
    
    /**
     * Tests nested draggable tables through keyboard.
     */
    public function testNestedDraggableTables() : void {
        $this->state
            ->set('tabledrag_test_table', array_flip(range(1, 5)));
        $this->drupalGet('tabledrag_test_nested');
        $this->assertKeyboardAccessibility('');
        // Now move the rows of the parent table.
        $expected_parent_table = [
            [
                'id' => 'parent_1',
                'weight' => 0,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            [
                'id' => 'parent_2',
                'weight' => 0,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            [
                'id' => 'parent_3',
                'weight' => 0,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
        ];
        $this->assertDraggableTable($expected_parent_table, 'tabledrag-test-parent-table', TRUE);
        // Switch parent table rows children.
        $this->moveRowWithKeyboard($this->findRowById('parent_2', 'tabledrag-test-parent-table'), 'up');
        $expected_parent_table = [
            [
                'id' => 'parent_2',
                'weight' => -10,
                'parent' => '',
                'indentation' => 0,
                'changed' => TRUE,
            ],
            [
                'id' => 'parent_1',
                'weight' => -9,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            [
                'id' => 'parent_3',
                'weight' => -8,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
        ];
        $this->assertDraggableTable($expected_parent_table, 'tabledrag-test-parent-table', TRUE);
        // Try to move the row that contains the nested table to the last position.
        // Order should be changed, but changed marker isn't added.
        // This seems to be buggy, but this is the original behavior.
        $this->moveRowWithKeyboard($this->findRowById('parent_1', 'tabledrag-test-parent-table'), 'down');
        $expected_parent_table = [
            [
                'id' => 'parent_2',
                'weight' => -10,
                'parent' => '',
                'indentation' => 0,
                'changed' => TRUE,
            ],
            [
                'id' => 'parent_3',
                'weight' => -9,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            // Since 'parent_1' row was moved, it should be marked as changed, but
            // this would fail with core tabledrag.js.
[
                'id' => 'parent_1',
                'weight' => -8,
                'parent' => '',
                'indentation' => 0,
                'changed' => NULL,
            ],
        ];
        $this->assertDraggableTable($expected_parent_table, 'tabledrag-test-parent-table', TRUE);
        // Re-test the nested draggable table.
        $expected_child_table_structure = [
            [
                'id' => '5',
                'weight' => -10,
                'parent' => '',
                'indentation' => 0,
                'changed' => FALSE,
            ],
            [
                'id' => '3',
                'weight' => -10,
                'parent' => '5',
                'indentation' => 1,
                'changed' => TRUE,
            ],
            [
                'id' => '1',
                'weight' => -9,
                'parent' => '',
                'indentation' => 0,
                'changed' => TRUE,
            ],
            [
                'id' => '2',
                'weight' => -10,
                'parent' => '1',
                'indentation' => 1,
                'changed' => TRUE,
            ],
            [
                'id' => '4',
                'weight' => -10,
                'parent' => '2',
                'indentation' => 2,
                'changed' => TRUE,
            ],
        ];
        $this->assertDraggableTable($expected_child_table_structure);
    }
    
    /**
     * 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.
     * @param string $table_id
     *   The ID of the table. Defaults to 'tabledrag-test-table'.
     * @param bool $skip_missing
     *   Whether assertions done on missing elements value may be skipped or not.
     *   Defaults to FALSE.
     *
     * @internal
     */
    protected function assertDraggableTable(array $structure, string $table_id = 'tabledrag-test-table', bool $skip_missing = FALSE) : void {
        $rows = $this->getSession()
            ->getPage()
            ->findAll('xpath', "//table[@id='{$table_id}']/tbody/tr");
        $this->assertSession()
            ->elementsCount('xpath', "//table[@id='{$table_id}']/tbody/tr", count($structure));
        foreach ($structure as $delta => $expected) {
            $this->assertTableRow($rows[$delta], $expected['id'], $expected['weight'], $expected['parent'], $expected['indentation'], $expected['changed'], $skip_missing);
        }
    }
    
    /**
     * 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|null $changed
     *   Whether or not the row should have been marked as changed. NULL means
     *   that this assertion should be skipped.
     * @param bool $skip_missing
     *   Whether assertions done on missing elements value may be skipped or not.
     *   Defaults to FALSE.
     *
     * @internal
     */
    protected function assertTableRow(NodeElement $row, string $id, int $weight, string $parent = '', int $indentation = 0, ?bool $changed = FALSE, bool $skip_missing = FALSE) : void {
        // Assert that the row position is correct by checking that the id
        // corresponds.
        $id_name = "table[{$id}][id]";
        if (!$skip_missing || $row->find('hidden_field_selector', [
            'hidden_field',
            $id_name,
        ])) {
            $this->assertSession()
                ->hiddenFieldValueEquals($id_name, $id, $row);
        }
        $parent_name = "table[{$id}][parent]";
        if (!$skip_missing || $row->find('hidden_field_selector', [
            'hidden_field',
            $parent_name,
        ])) {
            $this->assertSession()
                ->hiddenFieldValueEquals($parent_name, $parent, $row);
        }
        $this->assertSession()
            ->fieldValueEquals("table[{$id}][weight]", $weight, $row);
        $this->assertSession()
            ->elementsCount('xpath', static::$indentationXpathSelector, $indentation, $row);
        // A row is marked as changed when the related markup is present.
        if ($changed !== NULL) {
            $this->assertSession()
                ->elementsCount('xpath', static::$tabledragChangedXpathSelector, (int) $changed, $row);
        }
    }
    
    /**
     * Finds a row in the test table by the row ID.
     *
     * @param string $id
     *   The ID of the row.
     * @param string $table_id
     *   The ID of the parent table. Defaults to 'tabledrag-test-table'.
     *
     * @return \Behat\Mink\Element\NodeElement
     *   The row element.
     */
    protected function findRowById($id, $table_id = 'tabledrag-test-table') {
        $xpath = "//table[@id='{$table_id}']/tbody/tr[.//input[@name='table[{$id}][id]']]";
        $row = $this->getSession()
            ->getPage()
            ->find('xpath', $xpath);
        $this->assertNotEmpty($row);
        return $row;
    }
    
    /**
     * Finds the show/hide weight toggle element.
     *
     * @param string $expected_text
     *   The expected text on the element.
     *
     * @return \Behat\Mink\Element\NodeElement
     *   The toggle element.
     */
    protected function findWeightsToggle($expected_text) {
        $toggle = $this->getSession()
            ->getPage()
            ->findButton($expected_text);
        $this->assertNotEmpty($toggle);
        return $toggle;
    }
    
    /**
     * 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
     *   (optional) How many times to press the arrow button. Defaults to 1.
     */
    protected function moveRowWithKeyboard(NodeElement $row, $arrow, $repeat = 1) {
        $keys = [
            'left' => 37,
            'right' => 39,
            'up' => 38,
            'down' => 40,
        ];
        if (!isset($keys[$arrow])) {
            throw new \InvalidArgumentException('The arrow parameter must be one of "left", "right", "up" or "down".');
        }
        $key = $keys[$arrow];
        $handle = $row->find('css', 'a.tabledrag-handle');
        $handle->focus();
        for ($i = 0; $i < $repeat; $i++) {
            $this->markRowHandleForDragging($handle);
            $handle->keyDown($key);
            $handle->keyUp($key);
            $this->waitUntilDraggingCompleted($handle);
        }
        $handle->blur();
    }
    
    /**
     * Marks a row handle for dragging.
     *
     * The handle is marked by adding a css class that is removed by an helper
     * js library once the dragging is over.
     *
     * @param \Behat\Mink\Element\NodeElement $handle
     *   The draggable row handle element.
     *
     * @throws \Exception
     *   Thrown when the class is not added successfully to the handle.
     */
    protected function markRowHandleForDragging(NodeElement $handle) {
        $class = self::DRAGGING_CSS_CLASS;
        $script = <<<JS
document.evaluate("{<span class="php-variable">$handle</span>-&gt;<span class="php-function-or-constant function member-of-variable">getXpath</span>()}", document, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null)
  .singleNodeValue.classList.add('{<span class="php-variable">$class</span>}');
JS;
        $this->getSession()
            ->executeScript($script);
        $has_class = $this->getSession()
            ->getPage()
            ->waitFor(1, function () use ($handle, $class) {
            return $handle->hasClass($class);
        });
        if (!$has_class) {
            throw new \Exception(sprintf('Dragging css class was not added on handle "%s".', $handle->getXpath()));
        }
    }
    
    /**
     * Waits until the dragging operations are finished on a row handle.
     *
     * @param \Behat\Mink\Element\NodeElement $handle
     *   The draggable row handle element.
     *
     * @throws \Exception
     *   Thrown when the dragging operations are not completed on time.
     */
    protected function waitUntilDraggingCompleted(NodeElement $handle) {
        $class_removed = $this->getSession()
            ->getPage()
            ->waitFor(1, function () use ($handle) {
            return !$handle->hasClass($this::DRAGGING_CSS_CLASS);
        });
        if (!$class_removed) {
            throw new \Exception(sprintf('Dragging operations did not complete on time on handle %s', $handle->getXpath()));
        }
    }

}