Unable to test controller using Action.async

Question

I'm trying to test controller, which is using new Action.async. Following documentation I have excluded part under controller I want to test to separate trait with type reference:

trait UserController { this: Controller =>
  def index() = Action { /* snip */ }
  def register() = Action.async(parse.json) { request => /* snip */ }
}

Documentation states that I'm supposed to test it as:

object UsersControllerSpec extends PlaySpecification with Results {
  class TestController() extends Controller with UserController
    "index action" should {
      "should be valid" in {
        val controller = new TestController()
        val result: Future[SimpleResult] = controller.index().apply(FakeRequest())
        /* assertions */
      }
    }
  }
}

For index() method it works perfectly, unfortunately I'm not able to do the same with register(), as applying FakeRequest on it returns instance of Iteratee[Array[Byte], SimpleResult]. I've noticed it has run() method that returns Future[SimpleResult] but no matter how I build FakeRequest it returns with 400 without any content or headers. Seems to me like content of FakeRequest is disregarded at all. Am I supposed to feed request body to iteratee somehow and then run it? I couldn't find any example how could I do that.

Answer 1

This problem arises because play.api.mvc.Action[A] contains these two apply methods:

// What you're hoping for
def apply(request: Request[A]): Future[Result]

// What actually gets called
def apply(rh: RequestHeader): Iteratee[Array[Byte], Result]

This arises because Request[A] extends RequestHeader, and the A in this case makes all the difference. If it's not the right type, you'll end up calling the wrong apply.

When you use ActionBuilder with a BodyParser[A], you create an Action[A]. As a result, you'll need a Request[A] to test. parse.json returns a BodyParser[JsValue], so you need a Request[JsValue].

// In FakeRequest object
def apply(): FakeRequest[AnyContentAsEmpty.type]

FakeRequest() doesn't get you the type you need. Fortunately:

// In FakeRequest class
def withBody[B](body: B): FakeRequest[B]

So, start writing your test by using a placeholder for the body:

  "should be valid" in {
    val controller = new TestController()
    val body: JsValue = ??? // Change this once your test compiles

    // Could do these lines together, but this shows type signatures
    val request: Request[JsValue] = FakeRequest().withBody(body)
    val result: Future[Result] = controller.index().apply(request)

    /* assertions */
  }