class DateTestBase

abstract class DateTestBase extends BrowserTestBase {
    
    /**
     * {@inheritdoc}
     */
    protected static $modules = [
        'node',
        'entity_test',
        'datetime',
        'field_ui',
    ];
    
    /**
     * An array of display options.
     *
     * An array of display options to pass to
     * EntityDisplayRepositoryInterface::getViewDisplay()
     *
     * @var array
     *
     * @see \Drupal\Core\Entity\EntityDisplayRepositoryInterface::getViewDisplay()
     */
    protected $displayOptions;
    
    /**
     * A field storage to use in this test class.
     *
     * @var \Drupal\field\Entity\FieldStorageConfig
     */
    protected $fieldStorage;
    
    /**
     * The field used in this test class.
     *
     * @var \Drupal\field\Entity\FieldConfig
     */
    protected $field;
    
    /**
     * The date formatter service.
     *
     * @var \Drupal\Core\Datetime\DateFormatterInterface
     */
    protected $dateFormatter;
    
    /**
     * An array of timezone extremes to test.
     *
     * @var string[]
     */
    protected static $timezones = [
        // UTC-12, no DST.
'Pacific/Kwajalein',
        // UTC-11, no DST
'Pacific/Midway',
        // UTC-7, no DST.
'America/Phoenix',
        // UTC.
'UTC',
        // UTC+5:30, no DST.
'Asia/Kolkata',
        // UTC+12, no DST
'Pacific/Funafuti',
        // UTC+13, no DST.
'Pacific/Tongatapu',
    ];
    
    /**
     * Returns the type of field to be tested.
     *
     * @return string
     */
    protected abstract function getTestFieldType();
    
    /**
     * {@inheritdoc}
     */
    protected function setUp() : void {
        parent::setUp();
        $web_user = $this->drupalCreateUser([
            'access content',
            'view test entity',
            'administer entity_test content',
            'administer entity_test form display',
            'administer content types',
            'bypass node access',
            'administer node fields',
            'administer node form display',
            'administer node display',
        ]);
        $this->drupalLogin($web_user);
        // Create a field with settings to validate.
        $this->createField();
        $this->dateFormatter = $this->container
            ->get('date.formatter');
    }
    
    /**
     * Creates a date test field.
     */
    protected function createField() {
        $field_name = $this->randomMachineName();
        $field_label = Unicode::ucfirst($this->randomMachineName());
        $type = $this->getTestFieldType();
        $widget_type = $formatter_type = $type . '_default';
        $this->fieldStorage = FieldStorageConfig::create([
            'field_name' => $field_name,
            'entity_type' => 'entity_test',
            'type' => $type,
            'settings' => [
                'datetime_type' => DateTimeItem::DATETIME_TYPE_DATE,
            ],
        ]);
        $this->fieldStorage
            ->save();
        $this->field = FieldConfig::create([
            'field_storage' => $this->fieldStorage,
            'label' => $field_label,
            'bundle' => 'entity_test',
            'description' => 'Description for ' . $field_label,
            'required' => TRUE,
        ]);
        $this->field
            ->save();
        EntityFormDisplay::load('entity_test.entity_test.default')->setComponent($field_name, [
            'type' => $widget_type,
        ])
            ->save();
        $this->displayOptions = [
            'type' => $formatter_type,
            'label' => 'hidden',
            'settings' => [
                'format_type' => 'medium',
            ],
        ];
        EntityViewDisplay::create([
            'targetEntityType' => $this->field
                ->getTargetEntityTypeId(),
            'bundle' => $this->field
                ->getTargetBundle(),
            'mode' => 'full',
            'status' => TRUE,
        ])
            ->setComponent($field_name, $this->displayOptions)
            ->save();
    }
    
    /**
     * Renders an entity_test and sets the output in the internal browser.
     *
     * @param int $id
     *   The entity_test ID to render.
     * @param string $view_mode
     *   (optional) The view mode to use for rendering. Defaults to 'full'.
     * @param bool $reset
     *   (optional) Whether to reset the entity_test controller cache. Defaults to
     *   TRUE to simplify testing.
     *
     * @return string
     *   The rendered HTML output.
     */
    protected function renderTestEntity($id, $view_mode = 'full', $reset = TRUE) {
        if ($reset) {
            $this->container
                ->get('entity_type.manager')
                ->getStorage('entity_test')
                ->resetCache([
                $id,
            ]);
        }
        $entity = EntityTest::load($id);
        $display = EntityViewDisplay::collectRenderDisplay($entity, $view_mode);
        $build = $display->build($entity);
        return (string) $this->container
            ->get('renderer')
            ->renderRoot($build);
    }
    
    /**
     * Sets the site timezone to a given timezone.
     *
     * @param string $timezone
     *   The timezone identifier to set.
     */
    protected function setSiteTimezone($timezone) {
        // Set an explicit site timezone, and disallow per-user timezones.
        $this->config('system.date')
            ->set('timezone.user.configurable', 0)
            ->set('timezone.default', $timezone)
            ->save();
    }
    
    /**
     * Massages test date values.
     *
     * If a date object is generated directly by a test, then it needs to be
     * adjusted to behave like the computed date from the item.
     *
     * @param \Drupal\Core\Datetime\DrupalDateTime $date
     *   A date object directly generated by the test.
     */
    protected function massageTestDate($date) {
        if ($this->field
            ->getSetting('datetime_type') === DateTimeItem::DATETIME_TYPE_DATE) {
            // Set the default time for date-only items.
            $date->setDefaultDateTime();
        }
    }

}