code: public function getAdapter()
      {
          if (is_null($this->adapter)) {
              $name = ucfirst(strtolower($this->get('adapter')));
              $class = '\\Humbug\\Adapter\\' . $name;
              $this->adapter = new $class;
          }
          return $this->adapter;
      }
docs: Get a test framework adapter. Creates a new one based on the configured
  adapter name passed on the CLI if not already set.
  
  @return \Humbug\Adapter\AdapterAbstract