How to test Grails service using Spock?

Question

I have a EncouragementService.groovy with following method

  class EncouragementService {
   def stripePaymentService 

   def encourageUsers(List<User> users){
     if(null != users && users.size()>0){
      for(User user : users){
        //logic
        stripePaymentService.encourage(user)
        //
      }
     }   
   }
  }

To test above code in JAVA universe, using JUnit I would first create two or three users in setup. Pass the list of users to encourageUsers(...) method and check whatever I want with the result.

How can I achieve the same thing here in grails,

import com.github.jmkgreen.morphia.Datastore;

@TestFor(EncouragementService)
class EncouragementServiceSpec {

  def morphiaService = new MorphiaService()

  void testEncourageUsers() {
        List<User> users = createUsers();
        encouragementService.(users)  
            //
  }

  def createUsers(){
       Datastore datastore = morphiaService.dataStoreInstance()
       def user = new User()
       user.setName("Prayag Upd")
       //
       datastore.save(user)
       [user]
  }
}

I am using spock:0.7

plugins {
    test(":spock:0.7") { exclude "spock-grails-support" }
}

Answer 1

Service class can be optimized as below:

class EncouragementService {
   def encourageUsers(List<User> users){
       if(users){ //Groovy truth takes care of all the checks
          for(user in users){
            //logic
          }
       }   
   }
}

Spock Unit Test:
Spock takes testing to whole another level, where you can test the behavior (adheres to BDD). The test class would look like:

import spock.lang.*

@TestFor(EncouragementService)
@Mock(User) //If you are accessing User domain object.
class EncouragementServiceSpec extends Specification{
  //def encouragementService //DO NOT NEED: mocked in @TestFor annotation

  void "test Encourage Users are properly handled"() {
      given: "List of Users"
          List<User> users = createUsers()

      when: "service is called"
          //"service" represents the grails service you are testing for
          service.encourageUsers(users) 

      then: "Expect something to happen"
          //Assertion goes here
  }

  private def createUsers(){
       return users //List<User>
  }
}