Difficulties using Grails PageRenderer in service

I created a simple integration test for a service using a template. Basically, pass some kind of model to the GSP and render it, with the test comparing against a simple string. Sounds easy. All the examples of this usage seem to be consistent, but I get an NPE when I execute it. Many of the examples on the web used no constructor, but since that obviously won't work on the third line of code, I did a new on it, and tried to add a GroovyPagesTemplateEngine as well, in the end.

Here's the service code:

Code:

---

def listApprovals(userSso) {

                PageRenderer groovyPageRenderer = new PageRenderer()
                def results // no need for the code here, just passing a null for now
                groovyPageRenderer.render template: '/policy/approval', model: [approvals: results]
}

---

And here's the silly simple template:

Code:

---

// _approval.gsp
Here are your approvals ${approvals}

---

I get a null pointer exception as follows: In the PageRenderer class, there is an expectation set:

Code:

---

private void renderViewToWriter(Map args, Writer writer) {
        def source = null
        if (args.view) {
          source = groovyPageLocator.findViewByPath(args.view.toString())
        }
        else if (args.template) {
            source = groovyPageLocator.findTemplateByPath(args.template.toString())
        }

---

the variable groovyPageLocator is null, so it's obvious that I'm constructing that PageRenderer class wrongly. or the groovyPageLocator does not get properly injected when the service is initialized.

I need your thoughts.

Brian