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.
   */
  public function __construct(array $values) {
    $values += array(
      'required' => TRUE,
      'multiple' => FALSE,
      'label' => NULL,
      'description' => NULL,
      'class' => 'Drupal\Core\Plugin\Context\ContextDefinition',
    );
    $class = $values['class'];
    $this->definition = new $class($values['value'], $values['required'], $values['multiple'], $values['label'], $values['description']);
  }