Error while executing Integration Test with JSON output

Question

Below is my action in the controller. I am to btest this action via an integration test. This would require me to mock the session objects as well. I have started with the integration test , but hve no luck with it.

def listData= {

    def playerId=session["playerId”]    

    tuneInstanceList = tuneService.calculateId(playerId)


    def listResult = [total: tuneInstanceList.size(), items: tuneInstanceList]

    render listResult as JSON;

}

Below is the CalculateId method in my service class:

List calculateId(String playerId) {

   try{ 
   //read the sql file  
        String playerSql = grailsApplication.mainContext.getResource('classpath:'     +         Constants.PLAYER_FILE).inputStream.text  

def sql = new groovy.sql.Sql(dataSource)                  

def params = [playerId:playerId]  
def tuneInstanceList = new ArrayList<Tune>()  

def results = sql.rows(playerSql, params)  

tuneInstanceList = results.each {  
    def tune = new Tune()  
    tune.setPlayerId  it.player_id    
    tuneInstanceList.add tune 
} 
return tuneInstanceList 

 }catch (Exception ex) { 
    log.error ex.message, ex 
    throw ex 
} 
//finally { 
    //sql.close() 
//} 

}

Below is the Integration Test that I wrote. This isn’t correct and I am not sure what I should be putting up here. Inputs?

    public void testQuery () {

    def myController = new TuneController()
    myController.request.contentType = "text/json"

    myController.tuneService = tuneService

    myController.listData()

    String actualJSON = myController.response.contentAsString

    assertNotNull(actualJSON)




}

I get the belwo error when I run the test.

Cannot get property 'request' on null object

java.lang.NullPointerException: Cannot get property 'request' on null object

Thoughts??