Spock test with Mocks of Spring MVC Rest Controller using standaloneSetup and mockMvc

AccountControllerTest.groovy

import groovy.json.JsonSlurper
import org.springframework.test.web.servlet.MockMvc
import static org.springframework.test.web.servlet.setup.MockMvcBuilders.*
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
import static org.springframework.http.HttpStatus.*
import spock.lang.Specification

/**
 * A Spock Spring MVC Rest unit test that doesn't require a full spring context
 */
class AccountControllerTest extends Specification {
    def accountController = new AccountController()
    def securityService = Mock(SecurityService)

    //The magic happens here
    MockMvc mockMvc = standaloneSetup(accountController).build()

    def setup() {
        accountController.securityService = securityService
    }

    def "getAccount test hits the URL and parses JSON output"() {
        when: 'rest account url is hit'
        def response = mockMvc.perform(get('/rest/account')).andReturn().response
        def content = new JsonSlurper().parseText(response.contentAsString)

        then: 'securityService correctly returned account in JSON'
        1 * securityService.getCurrentLogin() >> 'spockUser'

        //Testing the HTTP Status code
        response.status == OK.value()

        //Showing how a contains test could work
        response.contentType.contains('application/json')
        response.contentType == 'application/json;charset=UTF-8'

        //Can test the whole content string that is returned
        response.contentAsString == '{"username":"spockUser"}'

        //Or can use the JsonSlurper version to test the JSON as object
        content.username == 'spockUser'
    }

    def "simple getAccount test without spring mvc json framework"() {
        when: 'getAccount is called'
        def result = accountController.getAccount()

        then: 'securityService correctly returns account'
        1 * securityService.getCurrentLogin() >> 'spockUser'

        result.username == 'spockUser'
    }
}

I did figure it out. It was not a request parameter we were using, just confusingly handling authentication.

Now I am battling IntelliJ and its autocomplete. I can't get my code to behave when using JSON-slurper...

Code compiles, test runs and passes, but IDE doesn't understand content.response.results[0].last4 == 1234

Seems not to know what the methods are.