Only for illustrative purposes, as seen in https://github.com/monix/monix/blob/master/monix-eval/shared/src/test/scala/monix/eval/TaskLocalSuite.scala

TaskLocalSuite.scala

import minitest.SimpleTestSuite
import monix.execution.Scheduler

object TaskLocalSuite extends SimpleTestSuite {
  implicit val ec: Scheduler = monix.execution.Scheduler.Implicits.global
  implicit val opts = Task.defaultOptions.enableLocalContextPropagation

  testAsync("Local.apply") {
    val test =
      for {
        local <- TaskLocal(0)
        v1 <- local.read
        _ <- Task.now(assertEquals(v1, 0))
        _ <- local.write(100)
        _ <- Task.shift
        v2 <- local.read
        _ <- Task.now(assertEquals(v2, 100))
        _ <- local.clear
        _ <- Task.shift
        v3 <- local.read
        _ <- Task.now(assertEquals(v3, 0))
      } yield ()

    test.runAsyncOpt
  }

  testAsync("Local.defaultLazy") {
    var i = 0

    val test =
      for {
        local <- TaskLocal.lazyDefault(Coeval { i += 1; i })
        v1 <- local.read
        _ <- Task.now(assertEquals(v1, 1))
        _ <- local.write(100)
        _ <- Task.shift
        v2 <- local.read
        _ <- Task.now(assertEquals(v2, 100))
        _ <- local.clear
        _ <- Task.shift
        v3 <- local.read
        _ <- Task.now(assertEquals(v3, 2))
      } yield ()

    test.runAsyncOpt
  }


  testAsync("TaskLocal!.bind") {
    val test =
      for {
        local <- TaskLocal(0)
        _ <- local.write(100)
        _ <- Task.shift
        v1 <- local.bind(200)(local.read.map(_ * 2))
        _ <- Task.now(assertEquals(v1, 400))
        v2 <- local.read
        _ <- Task.now(assertEquals(v2, 100))
      } yield ()

    test.runAsyncOpt
  }

  testAsync("TaskLocal!.bindL") {
    val test =
      for {
        local <- TaskLocal(0)
        _ <- local.write(100)
        _ <- Task.shift
        v1 <- local.bindL(Task.eval(200))(local.read.map(_ * 2))
        _ <- Task.now(assertEquals(v1, 400))
        v2 <- local.read
        _ <- Task.now(assertEquals(v2, 100))
      } yield ()

    test.runAsyncOpt
  }

  testAsync("TaskLocal!.bindClear") {
    val test =
      for {
        local <- TaskLocal(200)
        _ <- local.write(100)
        _ <- Task.shift
        v1 <- local.bindClear(local.read.map(_ * 2))
        _ <- Task.now(assertEquals(v1, 400))
        v2 <- local.read
        _ <- Task.now(assertEquals(v2, 100))
      } yield ()

    test.runAsyncOpt
  }
}