class ConfigurableTestClass

class ConfigurableTestClass extends PluginBase implements ConfigurableInterface {
    use ConfigurableTrait {
        defaultConfiguration as traitDefaultConfiguration;
    }
    
    /**
     * A default configuration for the test class to return.
     *
     * @var array|null
     */
    protected ?array $defaultConfiguration = NULL;
    
    /**
     * {@inheritdoc}
     */
    public function __construct(array $configuration = [], string $plugin_id = '', array $plugin_definition = []) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->setConfiguration($configuration);
    }
    
    /**
     * Sets the default configuration this test will return.
     *
     * @param array $default_configuration
     *   The default configuration to use.
     */
    public function setDefaultConfiguration(array $default_configuration) : void {
        $this->defaultConfiguration = $default_configuration;
    }
    
    /**
     * {@inheritdoc}
     */
    public function defaultConfiguration() : array {
        return $this->defaultConfiguration ?? $this->traitDefaultConfiguration();
    }

}