solved !!! it seems zendamf tries to find a class for the given "method" like this: if your source is given as "serviceTest" the plugin loader of zendamf tries to find it's parent class by making the first character UPPERCASE. So in my case it was trying to load the class named "ServiceTest" which does't exists. So i made the first character of my .php file UPPERCASE and it works !!!
I hope it will help someone else who's in same difficulties :)