// Unit test

def mockService = mockFor(MyService)

mockService.demand.myMethod { param, param -> return true; }

testController.myService = mockService.createMock();

testController.index([id:5,max;45]);



// Service object

class myService {

    def myMethod(param, param) {
        // doStuff
    }
}

// Controller object
class MyController {
    def myService;

    def index = {
        if(myService.myMethod(params.id, params.max)) {
            render('true');
        }else{
            render('false');
        }
    }
}