Unit testing web flow in Grails

I've used spock framework for my web flow controller unit test. Here is a pretty simple example:

/* SignUpControllerSpec.groovy */<br>@TestMixin(WebFlowUnitTestMixin)<br>@TestFor(SignUpController)<br>class SignUpControllerSpec extends Specification {<br><br>    def "test empty signup form submission"() {<br><br>        when: "user loads page with registration form"<br>            registerFlow.start.action()<br><br>        then: "empty userCommand object is created and lastEvent is start"<br>            lastEventName == 'start'<br>            flow.userCommand instanceof UserCommand<br><br>        when: "user submits the form with empty lines"<br>            registerFlow.signUp.on.submit.action()<br><br>        then: "userCommand with errors is returned"<br>            flow.userCommand.hasErrors()<br>            lastEventName == 'signUp'<br>            lastTransitionName == 'submit'<br>    }<br>}<br><br>/* SignUpController.groovy */<br>class SignUpController {<br><br>    def userService<br><br>    def registerFlow = {<br>        start {<br>            action {<br>                flow.userCommand = new UserCommand()<br>            }<br>            on('success').to('signUp')<br>        }<br><br>        signUp {<br>            on('submit') {<br>                bindData(flow.userCommand, params)<br>                def cmd = flow.userCommand<br>                if (!cmd.validate()) {<br>                    return error()<br>                }<br><br>                // TODO: process valid userCommand<br><br>            }.to('end')<br>        }<br><br>        end {<br>            redirect(uri: '/')<br>        }<br>    }<br>}