function wc_update_330_set_paypal_sandbox_credentials() {

	$paypal_settings = get_option( 'woocommerce_paypal_settings' );

	if ( isset( $paypal_settings['testmode'] ) && 'yes' === $paypal_settings['testmode'] ) {
		foreach ( array( 'api_username', 'api_password', 'api_signature' ) as $credential ) {
			if ( ! empty( $paypal_settings[ $credential ] ) ) {
				$paypal_settings[ 'sandbox_' . $credential ] = $paypal_settings[ $credential ];
			}
		}

		update_option( 'woocommerce_paypal_settings', $paypal_settings );
	}
}