FakeConsoleExample zio supplying a fake Console

FakeConsoleExample.scala

import zio._

object FakeConsoleExample extends ZIOAppDefault {

  private val program = ZIO.serviceWithZIO[Console] { console =>
    for {
      _     <- console.printLine("Going to the grocery store")
      input <- console.readLine("How are you? ")
      _     <- console.printLine(s"You said: $input")
    } yield ()
  }

  private val live = Console.ConsoleLive

  private val fakeConsoleLayer: ULayer[Console] = ZLayer.succeed(
    new Console {
      override def readLine(implicit trace: Trace): UIO[String] =
        ZIO.succeed(
          "I'm fine(this is canned)"
        )

      // Delegate all other methods to ConsoleLive, but always send to stderr
      override def print(line: => Any)(implicit trace: Trace) =
        live.printError(line)
      override def printError(line: => Any)(implicit trace: Trace) =
        live.printError(line)
      override def printLine(line: => Any)(implicit trace: Trace) =
        live.printLineError(line)
      override def printLineError(line: => Any)(implicit trace: Trace) =
        live.printLineError(line)
    }
  )

  override def run = program.provide(
    fakeConsoleLayer
  )
}

Output, all to stderr

Going to the grocery store
How are you? You said: I'm fine(this is canned)