trait BookTestTrait

trait BookTestTrait {
    
    /**
     * A book node.
     *
     * @var \Drupal\node\NodeInterface
     */
    protected $book;
    
    /**
     * A user with permission to create and edit books.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $bookAuthor;
    
    /**
     * Creates a new book with a page hierarchy.
     *
     * @param array $edit
     *   (optional) Field data in an associative array. Changes the current input
     *   fields (where possible) to the values indicated. Defaults to an empty
     *   array.
     *
     * @return \Drupal\node\NodeInterface[]
     */
    public function createBook($edit = []) {
        // Create new book.
        $this->drupalLogin($this->bookAuthor);
        $this->book = $this->createBookNode('new', NULL, $edit);
        $book = $this->book;
        
        /*
         * Add page hierarchy to book.
         * Book
         *  |- Node 0
         *   |- Node 1
         *   |- Node 2
         *  |- Node 3
         *  |- Node 4
         */
        $nodes = [];
        // Node 0.
        $nodes[] = $this->createBookNode($book->id(), NULL, $edit);
        // Node 1.
        $nodes[] = $this->createBookNode($book->id(), $nodes[0]->book['nid'], $edit);
        // Node 2.
        $nodes[] = $this->createBookNode($book->id(), $nodes[0]->book['nid'], $edit);
        // Node 3.
        $nodes[] = $this->createBookNode($book->id(), NULL, $edit);
        // Node 4.
        $nodes[] = $this->createBookNode($book->id(), NULL, $edit);
        $this->drupalLogout();
        return $nodes;
    }
    
    /**
     * Checks the outline of sub-pages; previous, up, and next.
     *
     * Also checks the printer friendly version of the outline.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   Node to check.
     * @param $nodes
     *   Nodes that should be in outline.
     * @param $previous
     *   Previous link node.
     * @param $up
     *   Up link node.
     * @param $next
     *   Next link node.
     * @param array $breadcrumb
     *   The nodes that should be displayed in the breadcrumb.
     */
    public function checkBookNode(EntityInterface $node, $nodes, $previous, $up, $next, array $breadcrumb) {
        // $number does not use drupal_static as it should not be reset
        // since it uniquely identifies each call to checkBookNode().
        static $number = 0;
        $this->drupalGet('node/' . $node->id());
        // Check outline structure.
        if ($nodes !== NULL) {
            $this->assertPattern($this->generateOutlinePattern($nodes));
        }
        else {
            $this->pass(new FormattableMarkup('Node %number does not have outline.', [
                '%number' => $number,
            ]));
        }
        // Check previous, up, and next links.
        if ($previous) {
            
            /** @var \Drupal\Core\Url $url */
            $url = $previous->toUrl();
            $url->setOptions([
                'attributes' => [
                    'rel' => [
                        'prev',
                    ],
                    'title' => t('Go to previous page'),
                ],
            ]);
            $text = new FormattableMarkup('<b>‹</b> @label', [
                '@label' => $previous->label(),
            ]);
            $this->assertRaw(Link::fromTextAndUrl($text, $url)->toString(), 'Previous page link found.');
        }
        if ($up) {
            
            /** @var \Drupal\Core\Url $url */
            $url = $up->toUrl();
            $url->setOptions([
                'attributes' => [
                    'title' => t('Go to parent page'),
                ],
            ]);
            $this->assertRaw(Link::fromTextAndUrl('Up', $url)->toString(), 'Up page link found.');
        }
        if ($next) {
            
            /** @var \Drupal\Core\Url $url */
            $url = $next->toUrl();
            $url->setOptions([
                'attributes' => [
                    'rel' => [
                        'next',
                    ],
                    'title' => t('Go to next page'),
                ],
            ]);
            $text = new FormattableMarkup('@label <b>›</b>', [
                '@label' => $next->label(),
            ]);
            $this->assertRaw(Link::fromTextAndUrl($text, $url)->toString(), 'Next page link found.');
        }
        // Compute the expected breadcrumb.
        $expected_breadcrumb = [];
        $expected_breadcrumb[] = Url::fromRoute('<front>')->toString();
        foreach ($breadcrumb as $a_node) {
            $expected_breadcrumb[] = $a_node->toUrl()
                ->toString();
        }
        // Fetch links in the current breadcrumb.
        $links = $this->xpath('//nav[@class="breadcrumb"]/ol/li/a');
        $got_breadcrumb = [];
        foreach ($links as $link) {
            $got_breadcrumb[] = $link->getAttribute('href');
        }
        // Compare expected and got breadcrumbs.
        $this->assertIdentical($expected_breadcrumb, $got_breadcrumb, 'The breadcrumb is correctly displayed on the page.');
        // Check printer friendly version.
        $this->drupalGet('book/export/html/' . $node->id());
        $this->assertText($node->label(), 'Printer friendly title found.');
        $this->assertRaw($node->body->processed, 'Printer friendly body found.');
        $number++;
    }
    
    /**
     * Creates a regular expression to check for the sub-nodes in the outline.
     *
     * @param array $nodes
     *   An array of nodes to check in outline.
     *
     * @return string
     *   A regular expression that locates sub-nodes of the outline.
     */
    public function generateOutlinePattern($nodes) {
        $outline = '';
        foreach ($nodes as $node) {
            $outline .= '(node\\/' . $node->id() . ')(.*?)(' . $node->label() . ')(.*?)';
        }
        return '/<nav id="book-navigation-' . $this->book
            ->id() . '"(.*?)<ul(.*?)' . $outline . '<\\/ul>/s';
    }
    
    /**
     * Creates a book node.
     *
     * @param int|string $book_nid
     *   A book node ID or set to 'new' to create a new book.
     * @param int|null $parent
     *   (optional) Parent book reference ID. Defaults to NULL.
     * @param array $edit
     *   (optional) Field data in an associative array. Changes the current input
     *   fields (where possible) to the values indicated. Defaults to an empty
     *   array.
     *
     * @return \Drupal\node\NodeInterface
     *   The created node.
     */
    public function createBookNode($book_nid, $parent = NULL, $edit = []) {
        // $number does not use drupal_static as it should not be reset
        // since it uniquely identifies each call to createBookNode().
        // Used to ensure that when sorted nodes stay in same order.
        static $number = 0;
        $edit['title[0][value]'] = str_pad($number, 2, '0', STR_PAD_LEFT) . ' - SimpleTest test node ' . $this->randomMachineName(10);
        $edit['body[0][value]'] = 'SimpleTest test body ' . $this->randomMachineName(32) . ' ' . $this->randomMachineName(32);
        $edit['book[bid]'] = $book_nid;
        if ($parent !== NULL) {
            $this->drupalPostForm('node/add/book', $edit, t('Change book (update list of parents)'));
            $edit['book[pid]'] = $parent;
            $this->drupalPostForm(NULL, $edit, t('Save'));
            // Make sure the parent was flagged as having children.
            $parent_node = \Drupal::entityTypeManager()->getStorage('node')
                ->loadUnchanged($parent);
            $this->assertFalse(empty($parent_node->book['has_children']), 'Parent node is marked as having children');
        }
        else {
            $this->drupalPostForm('node/add/book', $edit, t('Save'));
        }
        // Check to make sure the book node was created.
        $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
        $this->assertNotNull($node === FALSE ? NULL : $node, 'Book node found in database.');
        $number++;
        return $node;
    }

}