Change WooCommerce 3.0+ “has been added to cart” message

customize-add-to-cart-message.php

function mytheme_custom_add_to_cart_message($message, $product_id = null) {
  $titles[] = get_the_title( key($product_id));
  $titles = array_filter( $titles );
  $added_text = sprintf( _n( '%s has been added to cart.', '%s have been added to cart', sizeof( $titles ), 'woocommerce' ), wc_format_list_of_items( $titles ) ); //Change the message here

  $message = sprintf( '%s <a href="%s" class="button">%s</a>',
                  esc_html( $added_text ),
                  esc_url( wc_get_page_permalink( 'checkout' ) ), // Change to esc_url( wc_get_page_permalink( 'cart' ) ), if you want users to go to cart
                  esc_html__( 'Pay Now', 'woocommerce' ));

  return $message;
}
add_filter( 'wc_add_to_cart_message_html', 'mytheme_custom_add_to_cart_message', 10, 2 );