ZioWithRef.scala

import cats.data.{State, StateT}
import scalaz.zio._

type UserID = String
case class UserProfile(name:String)

trait Database {
  def lookup(id: UserID): Task[UserProfile]
  def update(id: UserID, profile: UserProfile): Task[Unit]
}

trait Logger {
  def info(id: String): Task[Unit]
}


sealed trait DBOp
final case class TestInstructionsState(ops: List[String])

trait TestService{
  val ref: Ref[TestInstructionsState]
}

trait DatabaseTestService extends Database with TestService {
  private var map: Map[UserID, UserProfile] = Map("abc" -> UserProfile("testName"))
  override val ref: Ref[TestInstructionsState]

  def lookup(id: UserID): Task[UserProfile] = {
    ref.update(x => x.copy(ops = "LookedUP"::x.ops)).map(_ => map(id))
  }
  def update(id: UserID, profile: UserProfile): Task[Unit] =
    ref.update(x => x.copy(ops = "Updated"::x.ops)).map(_ => map = map + (id -> profile))
}

trait LoggerTestService extends Logger with TestService {
  override val ref: Ref[TestInstructionsState]
  def info(id: String): Task[Unit] = ref.update(x => x.copy(ops = s"Logged - $id"::x.ops)).map(_ => ())
}

val runtime = new DefaultRuntime {}

val initialRef = runtime.unsafeRun(Ref.make(TestInstructionsState(Nil)))

object FinalEnv extends DatabaseTestService with LoggerTestService {
  override val ref = initialRef
}

val lookedUpProfile: ZIO[Database with Logger, Throwable, UserProfile] =
  for {
    profile <- ZIO.accessM[Database](x => x.lookup("abc"))
    _ <- ZIO.accessM[Logger](x => x.info(profile.name))
  } yield profile

val v = runtime.unsafeRun(lookedUpProfile.provide(FinalEnv))

runtime.unsafeRun(initialRef.get)