Play Framework Testing using MultipartFormData in a FakeRequest

Question

I am currently in the process of writing some Specs2 tests for may Play Framework 2.2.x application which accepts MultipartFormData submissions as part of it's function.

I have successfully written other tests with text and JSON bodies using the following form:

"respond to POST JSON with description field present" in {
  running(FakeApplication()) {
    val response = route(FakeRequest(POST, "/submission.json").withJsonBody(toJson(Map("content" -> toJson("test-content"), "description" -> toJson("test-description"))))).get
    status(response) must equalTo(OK)
    contentType(response) must beSome.which(_ == "application/json")
    contentAsString(response) must contain(""""description":"test-description"""")
    contentAsString(response) must contain(""""content":"test-content"""")
  }
}

However, when I use the .withMultipartFormData method I get the following errors:

Cannot write an instance of play.api.mvc.AnyContentAsMultipartFormData to HTTP response. Try to define a Writeable[play.api.mvc.AnyContentAsMultipartFormData]
val response = route(FakeRequest(PUT,"/submission.json/1/files").withMultipartFormDataBody(data)).get
                    ^

The MultipartFormData test I have been attempting to debug is of the form:

"respond to file PUT form with details not specififed" in {
  running(FakeApplication()) {
     val basePath:String = Play.application.path.getCanonicalPath();
     val data:MultipartFormData[TemporaryFile] = MultipartFormData(Map[String,Seq[String]](),
                                    List(
                                        FilePart("file_upload","",Some("Content-Type: multipart/form-data"),TemporaryFile(new java.io.File(basePath + "/test-data/testUpload.jpg")))
                                    ), 
                                    List(), 
                                    List())


     val response = route(FakeRequest(PUT,"/submission.json/1/files").withMultipartFormDataBody(data)).get
     status(response) must equalTo(CREATED)
 }
}

Looking at the Play Framework documentation for the relevant version of the FakeRequest class I can't see too much to help me trace down the problem: play.api.test.FakeRequest

And in terms of other documentation on the matter it seems the Play Framework website and Google are rather lacking.

I have tried the following alternative means of attempting to test my MultipartFormData code:

• Writing a test case for file uploads in Play 2.1 and Scala
• Test MultipartFormData in Play 2.0 FakeRequest
• How do I test multipart form data requests for file uploads in Play Framework 2.0 using Java? (Translating to Scala code first).

However, I have not had any success with any of these approaches either.

Answer 1

Rather than testing in a FakeApplication which is slow and (in my experience) can be error-prone when tests are running in parallel, I've been unit testing my Multipart form upload handlers like this:

1. Split out the Play wiring from your actual upload handling in your controller; e.g.:

   def handleUpload = Action(parse.multipartFormData) { implicit request =>
     doUpload(request)
   }
   
   def doUpload(request:Request[MultipartFormData[TemporaryFile]]) = {
     ...
   }
   

   (Where handleUpload is the method in your routes file that handles the POST)

2. Now you've got an endpoint that's easier to get at, you can mock out your service layer to respond appropriately to good/bad requests, and inject the mock service into your controller under test (I won't show that here, there are a million different ways to do that)

3. Now mock out a multipart request that will arrive at your doUpload method:

   val request= mock[Request[MultipartFormData[TemporaryFile]]]
   val tempFile = TemporaryFile("do_upload","spec")
   val fileName = "testFile.txt"
   val part = FilePart("key: String", fileName, None, tempFile)
   val files = Seq[FilePart[TemporaryFile]](part)
   val multipartBody = MultipartFormData(Map[String, Seq[String]](), files, Seq[BadPart](), Seq[MissingFilePart]())
   request.body returns multipartBody 
   

4. And finally, you can call your doUpload method and verify functionality:

   val result = controller.doUpload(request)
   status(result) must beEqualTo(201)
   

By testing like this, you can quickly and easily test all the error-handling paths in your Controller (which is probably what you're trying to do after all) without the overhead of needing to start the entire application.