An interesting way to use traits to enerate test cases in Scala

FibTests.scala

import org.scalatest.flatspec.AnyFlatSpec
import org.scalatest.matchers.should

import scala.annotation.tailrec
import scala.concurrent.{Await, Future}
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration._
import math.{pow, sqrt}

trait FibTest extends AnyFlatSpec with should.Matchers {

  def solutionName: String

  def fib(n: Int): Long

  solutionName should "compute correctly the value for 0 and 1" in {
    fib(0) should be(0)
    fib(1) should be(1)
  }

  it should "compute correctly the value for 2" in {
    fib(2) should be(1)
  }

  it should "compute correctly the value for 10" in {
    fib(10) should be(55)
  }

  it should "compute correctly the value for 100 within 10s" in {
    val futureResult = Future(fib(100))
    val result = Await.result(futureResult, 10.seconds)
    result should be(3736710778780434371L)
  }

}

class RecursiveSolutionTest extends FibTest {
  override def solutionName: String = "Recursive solution"

  def fib(n: Int): Long = n match {
    case 0 => 0
    case 1 => 1
    case n =>
      val x = fib(n-1)
      val y = fib(n-2)
      x + y
  }
}

class TailRecSolutionTest extends FibTest {
  override def solutionName: String = "Tail recursive solution"

  @tailrec
  final def tailRec(n: Int, a: Long = 0, b: Long = 1): Long = {
    if(n == 0) a
    else if (n == 1) b
    else tailRec(n-1, b, a+b)
  }

  def fib(n: Int): Long = tailRec(n)
}

class FormulaSolutionTest extends FibTest {
  override def solutionName: String = "Formula solution"

  def fib(n: Int): Long = {
    val fi = (1+sqrt(5))/2
    val psi = (1-sqrt(5))/2
    ((pow(fi,n) - pow(psi,n))/sqrt(5)).toLong
  }
}