I am developing a ws-bpel process using wso2 developer studio and I am following this Tutorial.
But when I want to deploy the Bpel process on the BusinessProcessServer, I am not able to test it. I get an empty interface.

I must have the request message to send it. I don't have any error in the bpel process when i generated it's .zip file.
Can any one help me please ?
Seems like it is because you have secured the service with UTOverTransport. Try unsecuring the service (Re-secure it later if needed).