How to use jUnit's TemporaryFolder in scala's specs2 tests?

Question

I'm writing a test with Playframework, and I need to create a temporary file.

@RunWith(classOf[JUnitRunner])
class DiagnosticSpec extends Specification {
  @Rule
  val temporaryFolder: TemporaryFolder = new TemporaryFolder()

  "my test" should {
     "run with temporary file" in {
        val file = temporaryFolder.newFile()   // line.35
        // go on with the file
     }
  }
}

But when I run this test, it always throw exception:

[error]     IllegalStateException: the temporary folder has not yet been created (MyTest.scala:35)

Is it possible to use it in specs2? If not, how can I create a temporary file in specs2, and delete it automatically after testing?

Answer 1

You cannot use JUnit rules with specs2 to do setup/teardown. You need to use AroundExample or FixtureExample for that:

trait TempFile extends AroundExample {
  // this code is executed "around" each example
  def around[R : AsResult](r: =>Result) = 
    val f = createFile("test")
    try AsResult(r)
    finally f.delete
}

class MySpec extends Specification with TempFile {
  "test" >> {
    // use the file here
    val file = new File("test")
    ...
  }
}

// Or
trait TempFile extends FixtureExample[File] {
  // this code is executed "around" each example
  def fixture[R : AsResult](f: File => R) = 
    val f = createFile("test")
    try AsResult(f(r))
    finally f.delete
}

class MySpec extends Specification with TempFile {
  // the file can be "injected" for each test
  "test" >> { file: File =>
    // use the file here
    ...
  }
}

UPDATE

The TemporaryFolder trait is closer to the original JUnit rule:

trait TemporaryFolder extends Specification {
  /** delete the temporary directory at the end of the specification */
  override def map(fs: => Fragments): Fragments = {
    super.map(fs.append(step(delete)))
  }

  lazy val tempDir = {
    val dir = File.createTempFile("test", "")
    dir.delete
    dir.mkdir
    dir
  }

  /** create a new file in the temp directory */
  def createNewFile = {
    val f = new File(tempDir.getPath+"/"+UUID.randomUUID.toString)
    f.createNewFile
    f
  }

  /** delete each file in the directory and the directory itself */
  def delete = {
    Option(tempDir.listFiles).map(_.toList).getOrElse(Nil).foreach(_.delete)
    tempDir.delete
  }
}

class MySpec extends Specification with TemporaryFolder {
  "test" >> {
    // use the file here
    val file = createNewFile
    ...
  }
}