Possible error in example code for Sharing fixtures across classes section

[Gavin Casey]

In the documentation there is some example code for

Sharing fixtures across classes

I was looking at this example with a view to applying it in my own tests but I am getting a compilation error with the example code 

... FixtureSharingTest.scala:35: recursive method withFixture needs result type

[error]       withFixture(test.toNoArgTest(db)) // "loan" the fixture to the test

Is there an error in the example code or is there something else I might need to take into account?

[Bill Venners]

Hi Gavin,

That's odd that it would think it is recursive. It is actually invoking an overloaded withFixture method that takes a NoArgTest. Anyway, you can always put the result type on. Instead of:

def withFixture(test: OneArgTest) = { ...

You can write:

def withFixture(test: OneArgTest): Outcome = {

I'll double check the example, but they all compile in our build. I wonder if you don't mind posting the exact class you're compiling and what the exact error message is.

Thanks.

Bill

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[Gavin Casey]

Hi Bill,

Isolating the code to a simple source file :

package com.xyz.ftest

import java.util.concurrent.ConcurrentHashMap

import org.scalatest._ //fixture

import DbServer._

import java.util.UUID.randomUUID

object DbServer { // Simulating a database server

  type Db = StringBuffer

    private val databases = new ConcurrentHashMap[String, Db]

      def createDb(name: String): Db = {

            val db = new StringBuffer

                databases.put(name, db)

                    db

                      }

        def removeDb(name: String) {

              databases.remove(name)

                }

}

trait DbFixture { this: fixture.Suite =>

  type FixtureParam = Db

// Allow clients to populate the database after

//   // it is created

   def populateDb(db: Db) {}

   def withFixture(test: OneArgTest): Outcome = {

     val dbName = randomUUID.toString

     val db = createDb(dbName) // create the fixture

     try {

       populateDb(db) // setup the fixture

       withFixture(test.toNoArgTest(db)) // "loan" the fixture to the test

     }

     finally removeDb(dbName) // clean up the fixture

     }

   }

class ExampleSpec extends fixture.WordSpec with DbFixture {

    override def populateDb(db: Db) { // setup the fixture

      db.append("ScalaTest is ")

    }

    "Testing" should {

      "should be easy" in { db =>

         db.append("easy!")

         assert(db.toString === "ScalaTest is easy!")

      }

      "should be fun" in { db =>

        db.append("fun!")

        assert(db.toString === "ScalaTest is fun!")

      }

   }

  // This test doesn't need a Db

  "Test code" should {

    "should be clear" in { () =>

    val buf = new StringBuffer

    buf.append("ScalaTest code is ")

    buf.append("clear!")

    assert(buf.toString === "ScalaTest code is clear!")

  }

 }

}

and compiling with scala 2.10.2

%scalac -cp ~/.ivy2/cache/org.scalatest/scalatest_2.10/jars/scalatest_2.10-2.0.M8.jar sharedfixture.scala 

Gives 

sharedfixture.scala:33: error: recursive method withFixture needs result type

       withFixture(test.toNoArgTest(db)) // "loan" the fixture to the test

Putting in the : Outcome return type fixes the above.

Regards,

Gavin

[Komsit Prakobphol]

I've found the same issue in version 2.2.6 in this scaladoc http://doc.scalatest.org/2.2.6/#org.scalatest.fixture.FunSpec. Adding return type ": Outcome" fixed the issue

package org.scalatest.examples.funspec.oneargtest

import org.scalatest.fixture
import java.io._

class ExampleSpec extends fixture.FunSpec {

  case class FixtureParam(file: File, writer: FileWriter)

  def withFixture(test: OneArgTest) = {

    // create the fixture
    val file = File.createTempFile("hello", "world")
    val writer = new FileWriter(file)
    val theFixture = FixtureParam(file, writer)

    try {
      writer.write("ScalaTest is ") // set up the fixture
      withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
    }
    finally writer.close() // clean up the fixture
  }

  describe("Testing") {
    it("should be easy") { f =>
      f.writer.write("easy!")
      f.writer.flush()
      assert(f.file.length === 18)
    }

    it("should be fun") { f =>
      f.writer.write("fun!")
      f.writer.flush()
      assert(f.file.length === 17)
    }
  }
}