[2.1.1-java] How can I mock async and Promises for testing

[EduP]

Hi,

We have some controllers that make async calls to a backend:

  public static Result foo() {
    // some previous code

    WSRequestHolder request = WS.url(backendUrl);

    return async(

      request.get().map(
        new Function<WS.Response, Result>() {
          public Result apply(WS.Response response) {
            // some callback code to process the response
            return ok(Json.toJson(someObject));

          }
        }
      )
    );
  }

In order to test them and work with TDD, we would like to write some tests that mock the backend invocations.

• Can we mock WSRequestHolder or WS.Response someway?
  
• I believe specs2 makes that possible for Scala. Can it be used with Java controllers?
  

Thanks in advance.

[ChrisDebug]

Hi!

Did you you ever get a solution for this?

[Eric Torreborre]

Did you try to use Mockito for this?

Eric.

[RandomSpark]

We have done Framework Wrappers i.e. any framework specific code e.g. WS or Messages are wrapped and we can easily mock the wrappers. For WS especially, we test the Wrapper with a dummy http service. This is a very common pattern so you can create a common library to be used across play projects.

Shripad

[ChrisDebug]

Thanks for the wrapping idea but I'm still not that clean on it. Do you think you can give me an example of wrapping WS.Response or point me to some urls that could help?

Is this the general idea?

public class WSResponseWrapper extends WS.Response {
    ...
}

[Alberto Souza]

This code is tricky to be mocked. It is a static call and libs around there, like Mockito, do not support this feature. Maybe PowerMock can help you. Here a example of code:

@RunWith(PowerMockRunner.class)

@PrepareForTest({ WS.class })

public class ApplicationTest {

  @Test

  public void mockWsCall() {

    mockStatic(WS.class);

     Mockito.when(WS.url("http://www.google.com")).thenReturn(new MyRequestHolder("http://www.google.com"));

    }

   public static class MyRequestHolder extends WSRequestHolder{

         public MyRequestHolder(String url) {

           super(url);

           System.out.println("my holder");

        }

    }

   }

In your build.sbt add the following lines:

  "org.powermock" % "powermock-core" % "1.5.4",

  "org.powermock" % "powermock-module-junit4" % "1.5.4",

  "org.powermock" % "powermock-api-mockito" % "1.5.4"

PowerMock is a nice alternative to mock Static behavior...

http://alots.wordpress.com
https://leanpub.com/playframeworknapratica

[Will Sargent]

I'd go for jMockit: https://code.google.com/p/jmockit/

You will be able to mock out WSRequest in 2.3, but for now the best thing you can do is to hide WS behind a service and mock out access to the service.  This will also help when you need to break apart your unit tests from your integration tests.

Will Sargent

Consultant, Professional Services

Typesafe, the company behind Play Framework, Akka and Scala

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[Alberto Souza]

Nice!. But, even with the service isolated in a class, the access still is static.

[Will Sargent]

On Fri, Feb 28, 2014 at 11:15 AM, Alberto Souza <alot...@gmail.com> wrote:

Nice!. But, even with the service isolated in a class, the access still is static.

It shouldn't be.

trait TwitterService {

  def getTweets : Future[Seq[Tweet]]

} 

class WSTwitterService extends TwitterService {

   def getTweets = {

       WS.url("...").get().map { response => parseTweets(response.json) }

   } 

}

class StubTwitterService extends TwitterService {

    def getTweets = { Future.successful(Tweet()) }

}

val stubTwitterService = new StubTwitterService()

val mockTwitterService = mock[TwitterService]

[ChrisDebug]

@Shripad: Thanks for the example! I'll definitely try this. I've been successfully using PowerMock for a few of my static methods so I'll try it here as well.

@Will: Thanks for the info as well. I can't wait for 2.3 to make my unit testing life easier. =)

[Chris]

How would I do this in 2.3?