ConstructorIssues.scala

package org.psi

class UnConstructableClass{
  
  
  dontExcept
  
  def dontExcept() { b.size}
  
  val b = List()
}


class DerivedClass(delayCall : Boolean) extends BaseClass(delayCall)
{
  start
  val b = List()
  def act() : Int = {b.size}
}

class DerivedClassB(delayCall : Boolean) extends BaseClass(delayCall)
{
  val b = List()
  start
  def act() : Int = {b.size}
}

abstract class BaseClass(delayCall: Boolean){
  implicit def asRunnable(func : ()=>unit) : Runnable = {new Runnable(){def run(){func()}}}
  
  def act() : Int  // abstract or overriden function
  var result : Int = -1;
  def start(){
    if(delayCall) {
      var t = new Thread(() => {
        try{
        	result = act()
        }catch{
          case n : NullPointerException => 
          result = -2;
        }
      })
      val r = new Random
      t.start
      if(r.nextBoolean())Thread.sleep(10)
    }
    else result = act()
  }
}

import org.scalatest.FunSuite
import org.scalatest.matchers.ShouldMatchers
import org.scalatest.junit.JUnitRunner
import org.junit.runner.RunWith
 
@RunWith(classOf[JUnitRunner])
class ConstuctorIssues extends FunSuite with ShouldMatchers{
    
	/// This test shows that the startup/teardown behavior is working without crashing
	test("Unconstrucable Class") {
	  intercept[NullPointerException]{
		new UnConstructableClass
	  }
	}
 
	test("Unconstructable Derived Class") {
	  intercept[NullPointerException]{
		new DerivedClass(false)
	  }
		
	}	
	test("raceCondition Derived Class"){
	  // this fails on my machine around 50% of the time, you might have to play with the timing
	  // to make it fail on you machine (or removed the random sleep) since it is a race condtion
	  val b = new DerivedClass(true)
	  Thread.sleep(3)
	  b.result should equal(0)

	}
 
	test("Valid Derived Class") {
	  new DerivedClassB(false)	
	}	
	test("Valid Derived Class immune to race conditions."){
	  val b = new DerivedClassB(true)
	  Thread.sleep(3)
	  b.result should equal(0)

	}
 
	
}