How to test (unit test) methods in spock which invloves rendering a view?

First of all, I haven't tried JUnit or any other testing framework so I hope you understand that I'm asking this kind of question.

I'm new to spock (and as I've already mentioned, I dont have any background any in testing frameworks) and I've created a simple app in grails. Now I want to create a code (unit test) to test the app that I made using spock (I hope you understand what I mean).

I've already read several articles about spock but I still don't have a good understanding of how to do it in my own app.

class DailyProfitController {
     def update() {
        params.date_month = (Integer.parseInt(params.date_month)<10)? "0" + params.date_month : params.date_month
        params.date_day = (Integer.parseInt(params.date_day)<10)? "0" + params.date_day : params.date_day
        params.date = params.date_year + "-" + params.date_month + "-" + params.date_day
        def dailyProfit = new DailyProfit(params)
        dailyProfit.save(flush:true, insert:false)
        list()    
    }


def list(){
    def dailyProfit = DailyProfit.list()
    render view:"profitTable",  model: [dailyProfit : dailyProfit]
}

}

Shown above is the controller and two methods, update and list. Assuming I want to create unit test code for this controller using spock, how will I do it?