Case class equals with list of byte array

Question

I am trying to use the should matchers on a case class

case class ListOfByteArrayCaseConfig(

  @BeanProperty 
  permissions: java.util.List[Array[Byte]]

)

With the following test case

val orig = ListOfByteArrayCaseConfig(List(Array[Byte](10, 20, 30)))
val orig2 = ListOfByteArrayCaseConfig(List(Array[Byte](10, 20, 30)))

orig2 should be === orig

Obviously this would fail because the two byte arrays are not equal reference wise. What I want to do is somehow make this work without changing the test case code and still keeping the case class.

Is it even possible? (like adding a custom equals method to the case class?)

Hanger

You are using ScalaTest or Specs2? – Courbet

Answer 1

I found the solution. Apparently I can override the equals method in a case class

Scala: Ignore case class field for equals/hascode?

Though it gets rid of the reason for using case classes in the first place which is to simplify data objects.

case class ListOfByteArrayCaseConfig(

  @BeanProperty 
  permissions: java.util.List[Array[Byte]]

) {

  override def equals(arg: Any): Boolean = {

    val obj = arg.asInstanceOf[ListOfByteArrayCaseConfig]
    var i: Int = 0
    for (i <- 0 until permissions.size()) {
      if (!util.Arrays.equals(permissions.get(i), obj.permissions.get(i))) {
        return false
      }
    }
    return true
  }
}

Hanger

+1, but you should not assume that object passed to equals() is of ListOfByteArrayCaseConfig type. Moreover, consider using pattern matching instead of downcasting. – Halfmoon

You had better override hashCode also if you plan on using this with sets or maps (or just want hashCode and equals to be consistent). – Slovenia

True, I just wanted a quick and dirty class to be used for testing, but I agree it needs a hashCode and a proper equals implementation. At the very least this shows what can be done. – Hanger

Answer 2

Linking this here as well.

Seems like it is a known issue - https://github.com/scalatest/scalatest/issues/491.

I worked around in an effective but maybe ugly way

  case class MyCaseClass(
    bytes: Array[Byte]
  )

  implicit val customEquality: Equality[MyCaseClass] = (a: MyCaseClass, b: Any) => b match {
    case exp: MyCaseClass =>
      exp.bytes.toSeq == a.bytes.toSeq && exp.copy(bytes = Array.empty) == a.copy(bytes = Array.empty)
    case _ => false
  }

Hellenic