hi all, I exposed a process model as a webservice. Can i use " ca

Not sure who provided that information, but that's not correct. You can totally test with the node and an instance will be created.

Selecting the WSDL in order to get the method will not initiate an instance. However, if you run the node that executes the WSDL, then a process instance for the target process model will be created.
And yes, you can test Appian process models exposed as web service using Appian web service node.

i tried several times, no instance was created.
i created a very simple model, only one process variable.
in the "Call web service" node. i passed username and password and that variable.
no error, no response, no instance.

Are you storing the Fault? in the node outputs

yes, but it only shows "[Object]", how can i see its real value?

To quickly see it simple go to /suite/designer click on the process then Process Details - Variables

If you use the Process Details - Variables tab it will show up fine there.

it says : SenderThis operation requires a username and password .
but i already configured the username and password

please see attached

is there anything wrong?