Grails + Spock: Testing Rendering views

index.gsp

Hi ${text}!

UserController.groovy

class UserController {
  def index(final String username) {
    flash.errors = "ops!"
    render view: "index", model: [username:username, text:username]
  }
}

UserControllerSpec.groovy

import grails.test.mixin.TestMixin
import spock.lang.Specification
import grails.test.mixin.web.GroovyPageUnitTestMixin

//@TestFor is replaced with the Mixin in the test
@TestMixin(GroovyPageUnitTestMixin)
class UserControllerSpec extends Specification {

  def controller

  def setup(){
    //The controller has to be mocked using testFor()
    controller = testFor(UserController)
  }

  void "test something"() {

    when:
      controller.index(username)

    then:
      flash.errors
      view == "/user/index"
      model.username == username

    and:
      //Method provided by mixin which mimics render method in controller.
      //Make sure model is also passed in the map arg
      render(view: "/user/index", model: model) == expectedOutput
      //or render(template: '/user/_template_name', model: model)

    where:
      username  || expectedOutput
      'goku'    || "Hi 'goku'!"
      'gohan'   || "Hi 'gohan'!"
      'kuririn' || "Hi 'kuririn'!"
  }
}
//reference: http://stackoverflow.com/a/23123835/1603694