How to tackle Magento development issues

I have a problem with debugging a thing (not a real error) in Magento (CE 1.4.1.1). For a payment module I've adapted, some additional payment fee is incorporated and is showing up on selection of the particular payment method. Works fine, no problems.

A client has the OneStepCheckout plugin installed. Inside it, the payment method works fine too (small problem: payment fee is showing up after the grand total, but that's not the issue, just for completeness of my question).

So, everything is working fine, even with some other payment modules installed. That is, working fine on dev and test! On the live 开发者_StackOverflow中文版server however, the extra fee does not show up! I've locally installed the other plugins that are installed on the live server as well, to see if there are any conflicts among them. None whatsoever. The Extension Conflict extension does not indicate any class overwriting problems either. Of course, I've cleared the cache. Several times.

So my question is a rather general one:

How to proceed?

What can I do and how to actually see what's going on and NOT break the live environment ? As far as I know, there is no staging server (there is a test server, but also there no error...), so I'm bound to the live environment.

Is there a common practice to handle these kind of issues? (And if so, what is it?)

I know of the MAGE_IS_DEVELOPER_MODE, system log, exception log etc, but since on dev everything works fine, I seem to not be able to really debug a bug which does not show up... can I safely switch on the logging on a live site by the way?

Thank you all in advance!

Regards,

Tom

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You can create your own log to see what is happening in Magento

Mage::log($datayouwanttosee, null, 'yourlogfile.log');

This will not break anything but will show you anything you want from that file. Once you load the page 'yourlogfile.log' will be in Magento's /var/log directory with the other log files.

Also make sure to turn your logging off when you are done otherwise the log could consume a lot of disk space.

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You have better results if you contact OneStepCheckout support directly with this issue. Also verify that you ar using the latest version of OneStepCheckout

Totals however have sort ordering and this is available in Magento admin under system > configuration > sales > sales > Checkout Totals Sort Order