Functional Rest API Testing with Grails/Rest Client Builder

Functional Rest API testing with Grails is easy and fun. We will be creating a simple Rest Controller and test it using Spock and Rest Client Builder.

When running the functional test a real container will be started on a specific port and tests are run against the running container. Just as it should be.

Performing a GET request on a url (http://localhost:8080/helloworld) should return a HTTP Status 200 and data with a json payload


So lets get started!

Create a Grails application

$ grails create-app RestHelloWorld

Update your build.gradle to include the Rest Client Builder dependencies which we will need later on

dependencies {
    // add the following line to the 'dependencies' section
    testCompile "org.grails:grails-datastore-rest-client:4.0.7.RELEASE"

Create an Integration Test

$ grails create-integration-test HelloWorld

Create a test method inside the integration test

Open up the created HelloWorldControllerSpec inside the /src/integration-test/groovy/resthelloworld/ package

package resthelloworld

import grails.test.mixin.integration.Integration
import grails.transaction.*
import spock.lang.*

class HelloWorldSpec extends Specification {

    def setup() {

    def cleanup() {

    def "Ask for a nice HelloWorld"() {
        RestBuilder rest = new RestBuilder()

        RestResponse response = rest.get("http://localhost:8080/helloworld/")

        response.status == 200

        response.json.message == "helloworld"

Run your test

$ grails test-app

Offcourse this will fail as we do not have implement the controller yet.

Create a Rest controller

$ cd RestHelloWorld
$ grails create-controller HelloWorld

Note: The generation of the controller also create a Unit Test for the controller, default this test will fail. We are going to delete the generated Unit Test as we do not need it now. This test is located under the /src/test/ groovy package.

$ rm ./src/test/groovy/resthelloworld/HelloWorldControllerSpec.groovy

Implement the controller function that will return data

package resthelloworld

class HelloWorldController {

    def index() {
        render(status: 200, contentType: "application/json") {
            ["message" : "helloworld"]

Modify UrlMapping

In order to get our newly generated controller accessible via Rest we need to modify our UrlMappings.

class UrlMappings {

    static mappings = {
            constraints {
                // apply constraints here


        // add the line below
        "/helloworld/"  (controller: "helloWorld", action: "index", method: "GET")

Test your app

$ grails test-app

You should find that your tests are fine now :)

$ grails test-app

Total time: 2.054 secs
| Tests PASSED