Selecting Pop up modal dialogs - Testing

Hi all.

I am page testing the Sales Order Post method in NAV 2017. I am having trouble activating the pop up modal dialogs.

1. When I create a new Item, the "Select an item template" dialog appears, prompting me to select a template. I need to know how to do that in C/AL.
2. When I post the Sales Order, the "Ship - Invoice - Ship and Invoice" dialog appears, same as above.

Really the problem is how to access the dialogs themselves. I know I can use the <testpage>.OK.INVOKE method, but How do I get access to the dialog?

Any help would be greatly appreciated as I can't find much documentation on this