testing.php

<?php

  /**
   * Constructs a new context definition object.
   *
   * @param array $values
   *   An associative array with the following keys:
   *   - value: The required data type.
   *   - required: (optional) Whether the context definition is required.
   *   - multiple: (optional) Whether the context definition is multivalue.
   *   - label: (optional) The UI label of this context definition.
   *   - description: (optional) The UI description of this context definition.
   *   - class: (optional) A custom ContextDefinitionInterface class.
   * @throws \Exception
   */
  public function __construct(array $values) {
    $values += array(
      'required' => TRUE,
      'multiple' => FALSE,
      'label' => NULL,
      'description' => NULL,
    );
    if (isset($values['class']) && !in_array('Drupal\Core\Plugin\Context\ContextDefinitionInterface', class_implements($values['class']))) {
      throw new \Exception("ContextDefinition class must implement \\Drupal\\Core\\Plugin\\Context\\ContextDefinitionInterface.");
    }
    $class = isset($values['class']) ? $values['class'] : 'Drupal\Core\Plugin\Context\ContextDefinition';
    $this->definition = new $class($values['value'], $values['required'], $values['multiple'], $values['label'], $values['description']);
  }