Subscriptions test handler code. Adds a "Renew Subscription" button to the Admin Edit Order page for orders containing a subscription product, which when clicked causes the subscriptions renewal code to be fired. This can be added to functions.php

wc-subs-test-handle.php

<?php

add_action( 'woocommerce_order_actions_start', function() {

	global $post_id;

	$order = new WC_Order( $post_id );

	if ( class_exists( 'WC_Subscriptions_Order' ) && WC_Subscriptions_Order::order_contains_subscription( $order ) ) {

		?>
		<li class="wide" style="text-align: center;">
			<a class="button tips" href="<?php echo add_query_arg( array( 'wc_subscriptions_action' => 'renew' ) ); ?>" data-tip="<?php esc_attr_e( 'Renew this subscription' ); ?>" style="cursor: pointer !important;"><?php _e( 'Renew This Subscription' ); ?></a>
		</li>
		<?php

	}
} );

add_action( 'admin_footer-post.php', function() {

	if ( isset( $_GET['wc_subscriptions_action'] ) && 'renew' == $_GET['wc_subscriptions_action'] ) {

		$order = new WC_Order( $_GET['post'] );

		$subscription = WC_Subscriptions_Manager::get_subscription( WC_Subscriptions_Manager::get_subscription_key( $order->id ) );

		$order = new WC_Order( $subscription['order_id'] );

		$amount_to_charge = WC_Subscriptions_Order::get_recurring_total( $order );

		$outstanding_payments = WC_Subscriptions_Order::get_outstanding_balance( $order, $subscription['product_id'] );

		if ( $outstanding_payments > 0 )
			$amount_to_charge += $outstanding_payments;

		do_action( 'scheduled_subscription_payment_' . $order->payment_method, $amount_to_charge, $order, $subscription['product_id'] );

	}

});