public function _initialize() {
		$this->wd_host = sprintf( 'http://%s:%s@hub.browserstack.com/wd/hub', $this->config['username'], $this->config['access_key'] );

		$this->capabilities = $this->config['capabilities'];
		$this->capabilities[ \WebDriverCapabilityType::BROWSER_NAME ] = $this->config['browser'];
		if ( ! empty( $this->config['version'] ) ) {
			$this->capabilities[ \WebDriverCapabilityType::VERSION ] = $this->config['version'];
		}

		$this->webDriver = \RemoteWebDriver::create( $this->wd_host, $this->capabilities );
		$this->webDriver->manage()->timeouts()->implicitlyWait( $this->config['wait'] );

		$this->initialWindowSize();
	}