Commission is applied off of all payments received. Commissions are a percentage. So, if the trial is a free trial, then there is no commission. However, if the trial is a small amount (like $1 trial for 3 days), then the commission is applied as a percentage of the amount of the trial payment. So, in our $1 trial example, if the commission is 20%, then the commission amount from the trial would be $0.20.
There is a report on the "Referral Program" page at the bottom of the page where you can see who has earned what and what payouts you need to make.
You need to manually do payouts. For PayPal and Payza there is an export to CSV option which allows you to make all of the payouts at once.
To test commission assignment without doing a real payment you will need to manually add a payment.
To add a payment manually, go to ~wmtsystemurl~/admin/members in the members area and click on the billing history icon for the member you want to add commission for.
In the popup click the Add Payment link.
Enter a payment amount and date. For Type and Transaction ID you can enter anything or leave blank as it doesn't affect test results.
To apply the payment visit: ~wmtsystemurl~/admin/applyaffiliatepayments.php