--- /dev/null
+<?php
+
+/**
+ * @file
+ * Test module for testing the book module.
+ *
+ * This module's functionality depends on the following state variables:
+ * - book_test.debug_book_navigation_cache_context: Used in NodeQueryAlterTest to enable the
+ * node_access_all grant realm.
+ *
+ * @see \Drupal\book\Tests\BookTest::testBookNavigationCacheContext()
+ */
+
+/**
+ * Implements hook_page_attachments().
+ */
+function book_test_page_attachments(array &$page) {
+ $page['#cache']['tags'][] = 'book_test.debug_book_navigation_cache_context';
+ if (\Drupal::state()->get('book_test.debug_book_navigation_cache_context', FALSE)) {
+ drupal_set_message(\Drupal::service('cache_contexts_manager')->convertTokensToKeys(['route.book_navigation'])->getKeys()[0]);
+ }
+}