Grails 2.2 functional test for a remote web service that requires JSON content in request

I am using Grails 2.2 and am writing a functional test for validating the JSON response received from a remote web service. The web service requires some JSON content to be passed in the request.

When I test this web service using a tool like "Postman", I receive the correct JSON response back.

I have written a functional test case in Grails 2.2 for this. Snippet of my sample code is provided below.

import com.grailsrocks.functionaltest.*
import com.grailsrocks.functionaltest.client.APIClient

class RemoteWebServiceFunctionalTests extends TestCaseBase{

  void testPost() {
        post("http://remoteAddress:8080/services/getData", {
            param1 = "value1"
            param2 = "value2"
            ...
            ...
            param3 = "value3"
        })

        assertStatus 200
    }

   @Override
   Class getDefaultClientType() {
     APIClient
   }

}

The output of running the test case is provided below for reference.

|Running 1 functional test... 1 of 1
--Output from testPost--
Switching to browser client [default]
Creating to new client [default] of type [class com.grailsrocks.functionaltest.client.APIClient]

== Making request POST http://remoteAddress:8080/services/getData parameters: ==
param1: value1
param2: value2
...
...
param3: value3

== Request headers: ============================================================
== Content =====================================================================

================================================================================
== Response was 200 (OK) headers: ==============================================
Server: Apache-Coyote/1.1
Content-Type: application/json
Content-Length: 148
Date: Fri, 27 Mar 2015 17:36:33 GMT
================================================================================
== Content =====================================================================
{"errors":[{"Error0001":"Invalid request. Please refer to API definition"}],"result":null,"warnings":null}
================================================================================

When I run the test, I do get the status 200 back but the correct JSON response content is not received. I think I am not formatting the request correctly. I need to know the correct way of supplying the JSON content to a remote web service call in a functional test case.

Any help in this regard is highly appreciated.