Tuesday, 6 August 2013

The elusive single FakeApplication specs2 test

As has been noted in numerous places, the Play 2 documentation on testing kinda suggests that spinning up a FakeApplication is something you can/should do in every single one of your test examples, e.g.:

  // Don't do this
class MyControllerSpec extends Specification {

  "My controller" should {

    "return a 404 on top-level GET to non-existent resource" in {
       running(FakeApplication()) {
         val home = route(FakeRequest(GET, "/mycontroller/blurg")).get
         status(home) must equalTo(NOT_FOUND)
       }
     }

     "serve up JSON on list request" in {
       running(FakeApplication()) {
         val home = route(FakeRequest(GET, "/mycontroller/list")).get
         status(home) must equalTo(OK)
         contentType(home) must beSome.which(_ == "application/json")
       }
     }
  }
}
Trust me when I say that it is not a good idea. At the very least slow tests, inconsistent test results and general Weird Things™ will happen.

What you most-likely want is something like this:
import play.api._
import play.api.test._
import org.specs2.specification._
import org.specs2.mutable._

/**
 * Mix this in to your Specification to spin up exactly one Play FakeApplication
 * that will be shut down after the last example has been run.
 * Override 'theApp' to use a customised FakeApplication
 */
trait FakePlayApplication {
  this: Specification =>

  def theApp = FakeApplication()

  def startApp = {
    System.err.println(s"Starting $theApp")
    Play.start(theApp)
  }

  def stopApp = {
    System.err.println(s"Stopping $theApp")
    Play.stop()
  }

  override def map(fs: => Fragments) = Step(startApp) ^ fs ^ Step(stopApp)
}

Which you could use in my previous example as follows:

class MyControllerSpec extends Specification with FakePlayApplication {

  "My controller" should {

    "return a 404 on top-level GET to non-existent resource" in {
         val home = route(FakeRequest(GET, "/mycontroller/blurg")).get
         status(home) must equalTo(NOT_FOUND)
     }

     "serve up JSON on list request" in {
         val home = route(FakeRequest(GET, "/mycontroller/list")).get
         status(home) must equalTo(OK)
         contentType(home) must beSome.which(_ == "application/json")
     }
  }
}
Less repetition, faster execution, and most importantly, RELIABLE TESTS!

No comments:

Post a Comment