diff --git a/CHANGELOG.org b/CHANGELOG.org
index bb87882..31c8187 100644
--- a/CHANGELOG.org
+++ b/CHANGELOG.org
@@ -6,6 +6,12 @@ The format is based on [[https://keepachangelog.com/en/1.0.0/][Keep a Changelog]
 [[https://semver.org/spec/v2.0.0.html][Semantic Versioning]].
 
 
+* [0.8.0] - 2019-??-??
+
+** Changed
+
+   - Replace cats-effect with zio (#117)
+
 * [0.7.2] - 2019-07-19
 
 ** Changed
diff --git a/build.sbt b/build.sbt
index 49898a7..4c16680 100644
--- a/build.sbt
+++ b/build.sbt
@@ -41,7 +41,7 @@ val testDependencies = Seq(
 val domainDependencies = Seq(
   libraryDependencies ++= Seq(
     "com.github.julien-truffaut"  %%  "monocle-core"    % "1.6.0",
-    "com.github.julien-truffaut"  %%  "monocle-macro"   % "1.6.0",
+    "com.github.julien-truffaut"  %%  "monocle-macro"   % "1.6.0"
   )
 )
 val commandLineParsing = Seq(
@@ -57,9 +57,9 @@ val awsSdkDependencies = Seq(
     "com.fasterxml.jackson.dataformat" % "jackson-dataformat-cbor" % "2.9.9"
   )
 )
-val catsEffectsSettings = Seq(
-  libraryDependencies ++=  Seq(
-    "org.typelevel" %% "cats-effect" % "1.3.1"
+val zioDependencies = Seq(
+  libraryDependencies ++= Seq (
+    "dev.zio" %% "zio" % "1.0.0-RC10-1"
   )
 )
 
@@ -110,6 +110,7 @@ lazy val core = (project in file("core"))
 
 lazy val `storage-api` = (project in file("storage-api"))
   .settings(commonSettings)
+  .settings(zioDependencies)
   .settings(assemblyJarName in assembly := "storage-api.jar")
   .dependsOn(domain)
 
@@ -117,5 +118,4 @@ lazy val domain = (project in file("domain"))
   .settings(commonSettings)
   .settings(domainDependencies)
   .settings(assemblyJarName in assembly := "domain.jar")
-  .settings(catsEffectsSettings)
   .settings(testDependencies)
diff --git a/cli/src/main/scala/net/kemitix/thorp/cli/Main.scala b/cli/src/main/scala/net/kemitix/thorp/cli/Main.scala
index 38814d5..f36cc5c 100644
--- a/cli/src/main/scala/net/kemitix/thorp/cli/Main.scala
+++ b/cli/src/main/scala/net/kemitix/thorp/cli/Main.scala
@@ -1,20 +1,14 @@
 package net.kemitix.thorp.cli
 
-import cats.effect.ExitCase.{Canceled, Completed, Error}
-import cats.effect.{ExitCode, IO, IOApp}
+import zio.{App, ZIO}
 
-object Main extends IOApp {
+object Main extends App {
 
-  override def run(args: List[String]): IO[ExitCode] = {
-    val exitCaseLogger = new PrintLogger(false)
-    ParseArgs(args)
-      .map(Program.run)
-      .getOrElse(IO(ExitCode.Error))
-      .guaranteeCase {
-        case Canceled  => exitCaseLogger.warn("Interrupted")
-        case Error(e)  => exitCaseLogger.error(e.getMessage)
-        case Completed => IO.unit
-      }
-  }
+  override def run(args: List[String]): ZIO[Environment, Nothing, Int] = {
+    for {
+      cliOptions <- ParseArgs(args)
+      _          <- Program.run(cliOptions)
+    } yield ()
+  }.fold(failure => 1, success => 0)
 
 }
diff --git a/cli/src/main/scala/net/kemitix/thorp/cli/ParseArgs.scala b/cli/src/main/scala/net/kemitix/thorp/cli/ParseArgs.scala
index 2527fd7..3042ff1 100644
--- a/cli/src/main/scala/net/kemitix/thorp/cli/ParseArgs.scala
+++ b/cli/src/main/scala/net/kemitix/thorp/cli/ParseArgs.scala
@@ -4,9 +4,17 @@ import java.nio.file.Paths
 
 import net.kemitix.thorp.core.{ConfigOption, ConfigOptions}
 import scopt.OParser
+import zio.Task
 
 object ParseArgs {
 
+  def apply(args: List[String]): Task[ConfigOptions] = Task {
+    OParser
+      .parse(configParser, args, List())
+      .map(ConfigOptions(_))
+      .getOrElse(ConfigOptions())
+  }
+
   val configParser: OParser[Unit, List[ConfigOption]] = {
     val parserBuilder = OParser.builder[List[ConfigOption]]
     import parserBuilder._
@@ -49,9 +57,4 @@ object ParseArgs {
     )
   }
 
-  def apply(args: List[String]): Option[ConfigOptions] =
-    OParser
-      .parse(configParser, args, List())
-      .map(ConfigOptions(_))
-
 }
diff --git a/cli/src/main/scala/net/kemitix/thorp/cli/PrintLogger.scala b/cli/src/main/scala/net/kemitix/thorp/cli/PrintLogger.scala
deleted file mode 100644
index af68c58..0000000
--- a/cli/src/main/scala/net/kemitix/thorp/cli/PrintLogger.scala
+++ /dev/null
@@ -1,25 +0,0 @@
-package net.kemitix.thorp.cli
-
-import cats.effect.IO
-import net.kemitix.thorp.domain.Logger
-
-class PrintLogger(isDebug: Boolean = false) extends Logger {
-
-  override def debug(message: => String): IO[Unit] =
-    if (isDebug) IO(println(s"[ DEBUG] $message"))
-    else IO.unit
-
-  override def info(message: => String): IO[Unit] =
-    IO(println(s"[  INFO] $message"))
-
-  override def warn(message: String): IO[Unit] =
-    IO(println(s"[  WARN] $message"))
-
-  override def error(message: String): IO[Unit] =
-    IO(println(s"[ ERROR] $message"))
-
-  override def withDebug(debug: Boolean): Logger =
-    if (isDebug == debug) this
-    else new PrintLogger(debug)
-
-}
diff --git a/cli/src/main/scala/net/kemitix/thorp/cli/Program.scala b/cli/src/main/scala/net/kemitix/thorp/cli/Program.scala
index a558b87..35d07e9 100644
--- a/cli/src/main/scala/net/kemitix/thorp/cli/Program.scala
+++ b/cli/src/main/scala/net/kemitix/thorp/cli/Program.scala
@@ -1,74 +1,79 @@
 package net.kemitix.thorp.cli
 
-import cats.effect.{ExitCode, IO}
-import cats.implicits._
 import net.kemitix.thorp.core._
-import net.kemitix.thorp.domain.{Logger, StorageQueueEvent}
+import net.kemitix.thorp.domain.{StorageQueueEvent, SyncTotals}
 import net.kemitix.thorp.storage.aws.S3HashService.defaultHashService
 import net.kemitix.thorp.storage.aws.S3StorageServiceBuilder.defaultStorageService
+import zio.console._
+import zio.{Task, TaskR, ZIO}
 
 trait Program extends PlanBuilder {
 
-  def run(cliOptions: ConfigOptions): IO[ExitCode] = {
-    implicit val logger: Logger = new PrintLogger()
-    if (ConfigQuery.showVersion(cliOptions))
-      for {
-        _ <- logger.info(s"Thorp v${thorp.BuildInfo.version}")
-      } yield ExitCode.Success
-    else
-      for {
-        syncPlan <- createPlan(
-          defaultStorageService,
-          defaultHashService,
-          cliOptions
-        ).valueOrF(handleErrors)
-        archive <- thorpArchive(cliOptions, syncPlan)
-        events  <- handleActions(archive, syncPlan)
-        _       <- defaultStorageService.shutdown
-        _       <- SyncLogging.logRunFinished(events)
-      } yield ExitCode.Success
+  lazy val version = s"Thorp v${thorp.BuildInfo.version}"
+
+  def run(cliOptions: ConfigOptions): ZIO[Console, Nothing, Unit] = {
+    val showVersion = ConfigQuery.showVersion(cliOptions)
+    for {
+      _ <- ZIO.when(showVersion)(putStrLn(version))
+      _ <- ZIO.when(!showVersion)(execute(cliOptions).catchAll(handleErrors))
+    } yield ()
   }
 
+  private def execute(
+      cliOptions: ConfigOptions): ZIO[Console, Throwable, Unit] = {
+    for {
+      plan    <- createPlan(defaultStorageService, defaultHashService, cliOptions)
+      archive <- thorpArchive(cliOptions, plan.syncTotals)
+      events  <- handleActions(archive, plan)
+      _       <- defaultStorageService.shutdown
+      _       <- SyncLogging.logRunFinished(events)
+    } yield ()
+  }
+
+  private def handleErrors(throwable: Throwable): ZIO[Console, Nothing, Unit] =
+    for {
+      _ <- putStrLn("There were errors:")
+      _ <- throwable match {
+        case ConfigValidationException(errors) =>
+          ZIO.foreach(errors)(error => putStrLn(s"- $error"))
+        case x => throw x
+      }
+    } yield ()
+
   def thorpArchive(
       cliOptions: ConfigOptions,
-      syncPlan: SyncPlan
-  ): IO[ThorpArchive] =
-    IO.pure(
-      UnversionedMirrorArchive.default(
-        defaultStorageService,
-        ConfigQuery.batchMode(cliOptions),
-        syncPlan.syncTotals
-      ))
-
-  private def handleErrors(
-      implicit logger: Logger
-  ): List[String] => IO[SyncPlan] = errors => {
-    for {
-      _ <- logger.error("There were errors:")
-      _ <- errors.map(error => logger.error(s" - $error")).sequence
-    } yield SyncPlan()
+      syncTotals: SyncTotals
+  ): Task[ThorpArchive] = Task {
+    UnversionedMirrorArchive.default(
+      defaultStorageService,
+      ConfigQuery.batchMode(cliOptions),
+      syncTotals
+    )
   }
 
   private def handleActions(
       archive: ThorpArchive,
       syncPlan: SyncPlan
-  )(implicit l: Logger): IO[Stream[StorageQueueEvent]] = {
-    type Accumulator = (Stream[IO[StorageQueueEvent]], Long)
+  ): TaskR[Console, Stream[StorageQueueEvent]] = {
+    type Accumulator = (Stream[StorageQueueEvent], Long)
     val zero: Accumulator = (Stream(), syncPlan.syncTotals.totalSizeBytes)
-    val (actions, _) = syncPlan.actions.zipWithIndex.reverse
-      .foldLeft(zero) { (acc: Accumulator, indexedAction) =>
-        {
-          val (stream, bytesToDo) = acc
+    TaskR
+      .foldLeft(syncPlan.actions.reverse.zipWithIndex)(zero)(
+        (acc, indexedAction) => {
           val (action, index)     = indexedAction
+          val (stream, bytesToDo) = acc
           val remainingBytes      = bytesToDo - action.size
-          (
-            archive.update(index, action, remainingBytes) ++ stream,
-            remainingBytes
-          )
-        }
+          (for {
+            event <- archive.update(index, action, remainingBytes)
+            events = stream ++ Stream(event)
+          } yield events)
+            .map((_, remainingBytes))
+        })
+      .map {
+        case (events, _) => events
       }
-    actions.sequence
   }
+
 }
 
 object Program extends Program
diff --git a/cli/src/test/scala/net/kemitix/thorp/cli/ParseArgsTest.scala b/cli/src/test/scala/net/kemitix/thorp/cli/ParseArgsTest.scala
index 253e905..bc94662 100644
--- a/cli/src/test/scala/net/kemitix/thorp/cli/ParseArgsTest.scala
+++ b/cli/src/test/scala/net/kemitix/thorp/cli/ParseArgsTest.scala
@@ -5,16 +5,19 @@ import java.nio.file.Paths
 import net.kemitix.thorp.core.ConfigOption.Debug
 import net.kemitix.thorp.core.{ConfigOptions, ConfigQuery, Resource}
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 import scala.util.Try
 
 class ParseArgsTest extends FunSpec {
 
+  private val runtime = new DefaultRuntime {}
+
   val source = Resource(this, "")
 
   describe("parse - source") {
     def invokeWithSource(path: String) =
-      ParseArgs(List("--source", path, "--bucket", "bucket"))
+      invoke(List("--source", path, "--bucket", "bucket"))
 
     describe("when source is a directory") {
       it("should succeed") {
@@ -31,7 +34,7 @@ class ParseArgsTest extends FunSpec {
         List("--source", "path1", "--source", "path2", "--bucket", "bucket")
       it("should get multiple sources") {
         val expected      = Some(Set("path1", "path2").map(Paths.get(_)))
-        val configOptions = ParseArgs(args)
+        val configOptions = invoke(args)
         val result        = configOptions.map(ConfigQuery.sources(_).paths.toSet)
         assertResult(expected)(result)
       }
@@ -42,7 +45,7 @@ class ParseArgsTest extends FunSpec {
     def invokeWithArgument(arg: String): ConfigOptions = {
       val strings = List("--source", pathTo("."), "--bucket", "bucket", arg)
         .filter(_ != "")
-      val maybeOptions = ParseArgs(strings)
+      val maybeOptions = invoke(strings)
       maybeOptions.getOrElse(ConfigOptions())
     }
 
@@ -71,4 +74,12 @@ class ParseArgsTest extends FunSpec {
       .map(_.getCanonicalPath)
       .getOrElse("[not-found]")
 
+  private def invoke(args: List[String]) =
+    runtime
+      .unsafeRunSync {
+        ParseArgs(args)
+      }
+      .toEither
+      .toOption
+
 }
diff --git a/cli/src/test/scala/net/kemitix/thorp/cli/ProgramTest.scala b/cli/src/test/scala/net/kemitix/thorp/cli/ProgramTest.scala
index 7e2834b..921dd30 100644
--- a/cli/src/test/scala/net/kemitix/thorp/cli/ProgramTest.scala
+++ b/cli/src/test/scala/net/kemitix/thorp/cli/ProgramTest.scala
@@ -3,16 +3,19 @@ package net.kemitix.thorp.cli
 import java.io.File
 import java.nio.file.Path
 
-import cats.data.EitherT
-import cats.effect.IO
 import net.kemitix.thorp.core.Action.{ToCopy, ToDelete, ToUpload}
 import net.kemitix.thorp.core._
+import net.kemitix.thorp.domain.StorageQueueEvent.DoNothingQueueEvent
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.{HashService, StorageService}
 import org.scalatest.FunSpec
+import zio.console.Console
+import zio.{DefaultRuntime, Task, TaskR}
 
 class ProgramTest extends FunSpec {
 
+  private val runtime = new DefaultRuntime {}
+
   val source: File     = Resource(this, ".")
   val sourcePath: Path = source.toPath
   val bucket: Bucket   = Bucket("aBucket")
@@ -35,36 +38,46 @@ class ProgramTest extends FunSpec {
     val archive = TestProgram.thorpArchive
     it("should be handled in correct order") {
       val expected = List(copyAction, uploadAction, deleteAction)
-      TestProgram.run(configOptions).unsafeRunSync
+      invoke(configOptions)
       val result = archive.actions
       assertResult(expected)(result)
     }
   }
 
+  private def invoke(configOptions: ConfigOptions) =
+    runtime.unsafeRunSync {
+      TestProgram.run(configOptions)
+    }.toEither
+
   trait TestPlanBuilder extends PlanBuilder {
-    override def createPlan(storageService: StorageService,
-                            hashService: HashService,
-                            configOptions: ConfigOptions)(
-        implicit l: Logger): EitherT[IO, List[String], SyncPlan] = {
-      EitherT.right(
-        IO(SyncPlan(Stream(copyAction, uploadAction, deleteAction))))
+    override def createPlan(
+        storageService: StorageService,
+        hashService: HashService,
+        configOptions: ConfigOptions
+    ): Task[SyncPlan] = {
+      Task(SyncPlan(Stream(copyAction, uploadAction, deleteAction)))
     }
   }
 
   class ActionCaptureArchive extends ThorpArchive {
     var actions: List[Action] = List[Action]()
-    override def update(index: Int, action: Action, totalBytesSoFar: Long)(
-        implicit l: Logger): Stream[IO[StorageQueueEvent]] = {
+    override def update(
+        index: Int,
+        action: Action,
+        totalBytesSoFar: Long
+    ): TaskR[Console, StorageQueueEvent] = {
       actions = action :: actions
-      Stream()
+      TaskR(DoNothingQueueEvent(RemoteKey("")))
     }
   }
 
   object TestProgram extends Program with TestPlanBuilder {
     val thorpArchive: ActionCaptureArchive = new ActionCaptureArchive
-    override def thorpArchive(cliOptions: ConfigOptions,
-                              syncPlan: SyncPlan): IO[ThorpArchive] =
-      IO.pure(thorpArchive)
+    override def thorpArchive(
+        cliOptions: ConfigOptions,
+        syncTotals: SyncTotals
+    ): Task[ThorpArchive] =
+      Task(thorpArchive)
   }
 
 }
diff --git a/core/src/main/scala/net/kemitix/thorp/core/ConfigOptions.scala b/core/src/main/scala/net/kemitix/thorp/core/ConfigOptions.scala
index 3b7a523..0fdd95f 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/ConfigOptions.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/ConfigOptions.scala
@@ -1,14 +1,13 @@
 package net.kemitix.thorp.core
 
-import cats.Semigroup
 import monocle.Lens
 import monocle.macros.GenLens
 
 case class ConfigOptions(
     options: List[ConfigOption] = List()
-) extends Semigroup[ConfigOptions] {
+) {
 
-  override def combine(
+  def combine(
       x: ConfigOptions,
       y: ConfigOptions
   ): ConfigOptions =
diff --git a/core/src/main/scala/net/kemitix/thorp/core/ConfigValidation.scala b/core/src/main/scala/net/kemitix/thorp/core/ConfigValidation.scala
index de9ad81..10a3c73 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/ConfigValidation.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/ConfigValidation.scala
@@ -1,5 +1,7 @@
 package net.kemitix.thorp.core
 
+import java.nio.file.Path
+
 sealed trait ConfigValidation {
 
   def errorMessage: String
@@ -19,4 +21,11 @@ object ConfigValidation {
     override def errorMessage: String = "Bucket name is missing"
   }
 
+  case class ErrorReadingFile(
+      path: Path,
+      message: String
+  ) extends ConfigValidation {
+    override def errorMessage: String = s"Error reading file '$path': $message"
+  }
+
 }
diff --git a/core/src/main/scala/net/kemitix/thorp/core/ConfigValidationException.scala b/core/src/main/scala/net/kemitix/thorp/core/ConfigValidationException.scala
new file mode 100644
index 0000000..37e4e20
--- /dev/null
+++ b/core/src/main/scala/net/kemitix/thorp/core/ConfigValidationException.scala
@@ -0,0 +1,5 @@
+package net.kemitix.thorp.core
+
+final case class ConfigValidationException(
+    errors: List[ConfigValidation]
+) extends Exception
diff --git a/core/src/main/scala/net/kemitix/thorp/core/ConfigValidator.scala b/core/src/main/scala/net/kemitix/thorp/core/ConfigValidator.scala
index a3222ed..0fdb2ce 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/ConfigValidator.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/ConfigValidator.scala
@@ -2,42 +2,57 @@ package net.kemitix.thorp.core
 
 import java.nio.file.Path
 
-import cats.data.{NonEmptyChain, Validated, ValidatedNec}
-import cats.implicits._
 import net.kemitix.thorp.domain.{Bucket, Config, Sources}
+import zio.IO
 
 sealed trait ConfigValidator {
 
-  type ValidationResult[A] = ValidatedNec[ConfigValidation, A]
-
   def validateConfig(
-      config: Config): Validated[NonEmptyChain[ConfigValidation], Config] =
-    (
-      validateSources(config.sources),
-      validateBucket(config.bucket)
-    ).mapN((_, _) => config)
+      config: Config
+  ): IO[List[ConfigValidation], Config] = IO.fromEither {
+    for {
+      _ <- validateSources(config.sources)
+      _ <- validateBucket(config.bucket)
+    } yield config
+  }
 
-  def validateBucket(bucket: Bucket): ValidationResult[Bucket] =
-    if (bucket.name.isEmpty) ConfigValidation.BucketNameIsMissing.invalidNec
-    else bucket.validNec
+  def validateBucket(bucket: Bucket): Either[List[ConfigValidation], Bucket] =
+    if (bucket.name.isEmpty) Left(List(ConfigValidation.BucketNameIsMissing))
+    else Right(bucket)
 
-  def validateSources(sources: Sources): ValidationResult[Sources] =
-    sources.paths
-      .map(validateSource)
-      .sequence
-      .map(_ => sources)
+  def validateSources(
+      sources: Sources): Either[List[ConfigValidation], Sources] =
+    (for {
+      x <- sources.paths.foldLeft(List[ConfigValidation]()) {
+        (acc: List[ConfigValidation], path) =>
+          {
+            validateSource(path) match {
+              case Left(errors) => acc ++ errors
+              case Right(_)     => acc
+            }
+          }
+      }
+    } yield x) match {
+      case Nil    => Right(sources)
+      case errors => Left(errors)
+    }
 
-  def validateSource(source: Path): ValidationResult[Path] =
-    validateSourceIsDirectory(source)
-      .andThen(s => validateSourceIsReadable(s))
+  def validateSource(source: Path): Either[List[ConfigValidation], Path] =
+    for {
+      _ <- validateSourceIsDirectory(source)
+      _ <- validateSourceIsReadable(source)
+    } yield source
 
-  def validateSourceIsDirectory(source: Path): ValidationResult[Path] =
-    if (source.toFile.isDirectory) source.validNec
-    else ConfigValidation.SourceIsNotADirectory.invalidNec
+  def validateSourceIsDirectory(
+      source: Path): Either[List[ConfigValidation], Path] =
+    if (source.toFile.isDirectory) Right(source)
+    else Left(List(ConfigValidation.SourceIsNotADirectory))
+
+  def validateSourceIsReadable(
+      source: Path): Either[List[ConfigValidation], Path] =
+    if (source.toFile.canRead) Right(source)
+    else Left(List(ConfigValidation.SourceIsNotReadable))
 
-  def validateSourceIsReadable(source: Path): ValidationResult[Path] =
-    if (source.toFile.canRead) source.validNec
-    else ConfigValidation.SourceIsNotReadable.invalidNec
 }
 
 object ConfigValidator extends ConfigValidator
diff --git a/core/src/main/scala/net/kemitix/thorp/core/ConfigurationBuilder.scala b/core/src/main/scala/net/kemitix/thorp/core/ConfigurationBuilder.scala
index 9d19da3..df50081 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/ConfigurationBuilder.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/ConfigurationBuilder.scala
@@ -2,12 +2,11 @@ package net.kemitix.thorp.core
 
 import java.nio.file.Paths
 
-import cats.data.NonEmptyChain
-import cats.effect.IO
+import net.kemitix.thorp.core.ConfigOptions.options
 import net.kemitix.thorp.core.ConfigValidator.validateConfig
 import net.kemitix.thorp.core.ParseConfigFile.parseFile
-import net.kemitix.thorp.core.ConfigOptions.options
 import net.kemitix.thorp.domain.Config
+import zio.IO
 
 /**
   * Builds a configuration from settings in a file within the
@@ -19,25 +18,31 @@ trait ConfigurationBuilder {
   private val globalConfig       = Paths.get("/etc/thorp.conf")
   private val userHome           = Paths.get(System.getProperty("user.home"))
 
-  def buildConfig(priorityOpts: ConfigOptions)
-    : IO[Either[NonEmptyChain[ConfigValidation], Config]] = {
-    val sources = ConfigQuery.sources(priorityOpts)
+  def buildConfig(
+      priorityOpts: ConfigOptions): IO[List[ConfigValidation], Config] =
     for {
-      sourceOpts <- SourceConfigLoader.loadSourceConfigs(sources)
+      config <- getConfigOptions(priorityOpts).map(collateOptions)
+      valid  <- validateConfig(config)
+    } yield valid
+
+  private def getConfigOptions(
+      priorityOpts: ConfigOptions): IO[List[ConfigValidation], ConfigOptions] =
+    for {
+      sourceOpts <- SourceConfigLoader.loadSourceConfigs(
+        ConfigQuery.sources(priorityOpts))
       userOpts   <- userOptions(priorityOpts ++ sourceOpts)
       globalOpts <- globalOptions(priorityOpts ++ sourceOpts ++ userOpts)
-      collected = priorityOpts ++ sourceOpts ++ userOpts ++ globalOpts
-      config    = collateOptions(collected)
-    } yield validateConfig(config).toEither
-  }
+    } yield priorityOpts ++ sourceOpts ++ userOpts ++ globalOpts
 
-  private val emptyConfig = IO(ConfigOptions())
+  private val emptyConfig = IO.succeed(ConfigOptions())
 
-  private def userOptions(priorityOpts: ConfigOptions) =
+  private def userOptions(
+      priorityOpts: ConfigOptions): IO[List[ConfigValidation], ConfigOptions] =
     if (ConfigQuery.ignoreUserOptions(priorityOpts)) emptyConfig
     else parseFile(userHome.resolve(userConfigFilename))
 
-  private def globalOptions(priorityOpts: ConfigOptions) =
+  private def globalOptions(
+      priorityOpts: ConfigOptions): IO[List[ConfigValidation], ConfigOptions] =
     if (ConfigQuery.ignoreGlobalOptions(priorityOpts)) emptyConfig
     else parseFile(globalConfig)
 
diff --git a/core/src/main/scala/net/kemitix/thorp/core/LocalFileStream.scala b/core/src/main/scala/net/kemitix/thorp/core/LocalFileStream.scala
index e7facd8..42ceca3 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/LocalFileStream.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/LocalFileStream.scala
@@ -2,53 +2,46 @@ package net.kemitix.thorp.core
 
 import java.nio.file.Path
 
-import cats.effect.IO
 import net.kemitix.thorp.core.KeyGenerator.generateKey
 import net.kemitix.thorp.domain
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.HashService
+import zio.Task
 
 object LocalFileStream {
 
-  private val emptyIOLocalFiles = IO.pure(LocalFiles())
-
   def findFiles(
       source: Path,
       hashService: HashService
   )(
-      implicit c: Config,
-      logger: Logger
-  ): IO[LocalFiles] = {
+      implicit c: Config
+  ): Task[LocalFiles] = {
 
     val isIncluded: Path => Boolean = Filter.isIncluded(c.filters)
 
-    val pathToLocalFile: Path => IO[LocalFiles] = path =>
-      localFile(hashService, logger, c)(path)
+    val pathToLocalFile: Path => Task[LocalFiles] = path =>
+      localFile(hashService, c)(path)
 
-    def loop(path: Path): IO[LocalFiles] = {
+    def loop(path: Path): Task[LocalFiles] = {
 
-      def dirPaths(path: Path) =
+      def dirPaths(path: Path): Task[Stream[Path]] =
         listFiles(path)
           .map(_.filter(isIncluded))
 
-      def recurseIntoSubDirectories(path: Path) =
+      def recurseIntoSubDirectories(path: Path): Task[LocalFiles] =
         path.toFile match {
           case f if f.isDirectory => loop(path)
           case _                  => pathToLocalFile(path)
         }
 
-      def recurse(paths: Stream[Path]) =
-        paths.foldLeft(emptyIOLocalFiles)(
-          (acc, path) =>
-            recurseIntoSubDirectories(path)
-              .flatMap(localFiles =>
-                acc.map(accLocalFiles => accLocalFiles ++ localFiles)))
+      def recurse(paths: Stream[Path]): Task[LocalFiles] =
+        Task.foldLeft(paths)(LocalFiles())((acc, path) => {
+          recurseIntoSubDirectories(path).map(localFiles => acc ++ localFiles)
+        })
 
       for {
-        _          <- logger.debug(s"- Entering: $path")
         paths      <- dirPaths(path)
         localFiles <- recurse(paths)
-        _          <- logger.debug(s"- Leaving : $path")
       } yield localFiles
     }
 
@@ -57,14 +50,13 @@ object LocalFileStream {
 
   def localFile(
       hashService: HashService,
-      l: Logger,
       c: Config
-  ): Path => IO[LocalFiles] =
+  ): Path => Task[LocalFiles] =
     path => {
       val file   = path.toFile
       val source = c.sources.forPath(path)
       for {
-        hash <- hashService.hashLocalObject(path)(l)
+        hash <- hashService.hashLocalObject(path)
       } yield
         LocalFiles(localFiles = Stream(
                      domain.LocalFile(file,
@@ -75,15 +67,11 @@ object LocalFileStream {
                    totalSizeBytes = file.length)
     }
 
-  //TODO: Change this to return an Either[IllegalArgumentException, Stream[Path]]
-  private def listFiles(path: Path) = {
-    IO(
-      Option(path.toFile.listFiles)
-        .map { fs =>
-          Stream(fs: _*)
-            .map(_.toPath)
-        }
-        .getOrElse(
-          throw new IllegalArgumentException(s"Directory not found $path")))
-  }
+  private def listFiles(path: Path): Task[Stream[Path]] =
+    for {
+      files <- Task(path.toFile.listFiles)
+      _ <- Task.when(files == null)(
+        Task.fail(new IllegalArgumentException(s"Directory not found $path")))
+    } yield Stream(files: _*).map(_.toPath)
+
 }
diff --git a/core/src/main/scala/net/kemitix/thorp/core/MD5HashGenerator.scala b/core/src/main/scala/net/kemitix/thorp/core/MD5HashGenerator.scala
index 76fe67f..3972846 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/MD5HashGenerator.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/MD5HashGenerator.scala
@@ -4,8 +4,8 @@ import java.io.{File, FileInputStream}
 import java.nio.file.Path
 import java.security.MessageDigest
 
-import cats.effect.IO
-import net.kemitix.thorp.domain.{Logger, MD5Hash}
+import net.kemitix.thorp.domain.MD5Hash
+import zio.Task
 
 import scala.collection.immutable.NumericRange
 
@@ -26,21 +26,19 @@ object MD5HashGenerator {
     md5.digest
   }
 
-  def md5File(path: Path)(implicit logger: Logger): IO[MD5Hash] =
+  def md5File(path: Path): Task[MD5Hash] =
     md5FileChunk(path, 0, path.toFile.length)
 
   def md5FileChunk(
       path: Path,
       offset: Long,
       size: Long
-  )(implicit logger: Logger): IO[MD5Hash] = {
+  ): Task[MD5Hash] = {
     val file      = path.toFile
     val endOffset = Math.min(offset + size, file.length)
     for {
-      _      <- logger.debug(s"md5:reading:size ${file.length}:$path")
       digest <- readFile(file, offset, endOffset)
       hash = MD5Hash.fromDigest(digest)
-      _ <- logger.debug(s"md5:generated:${hash.hash}:$path")
     } yield hash
   }
 
@@ -58,20 +56,20 @@ object MD5HashGenerator {
   private def openFile(
       file: File,
       offset: Long
-  ) = IO {
+  ) = Task {
     val stream = new FileInputStream(file)
     stream skip offset
     stream
   }
 
-  private def closeFile(fis: FileInputStream) = IO(fis.close())
+  private def closeFile(fis: FileInputStream) = Task(fis.close())
 
   private def digestFile(
       fis: FileInputStream,
       offset: Long,
       endOffset: Long
   ) =
-    IO {
+    Task {
       val md5 = MessageDigest getInstance "MD5"
       NumericRange(offset, endOffset, maxBufferSize)
         .foreach(currentOffset =>
diff --git a/core/src/main/scala/net/kemitix/thorp/core/ParseConfigFile.scala b/core/src/main/scala/net/kemitix/thorp/core/ParseConfigFile.scala
index fce315e..2d4bd07 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/ParseConfigFile.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/ParseConfigFile.scala
@@ -2,25 +2,29 @@ package net.kemitix.thorp.core
 
 import java.nio.file.{Files, Path}
 
-import cats.effect.IO
+import zio.{IO, Task}
 
 import scala.collection.JavaConverters._
 
 trait ParseConfigFile {
 
-  def parseFile(filename: Path): IO[ConfigOptions] =
+  def parseFile(filename: Path): IO[List[ConfigValidation], ConfigOptions] =
     readFile(filename)
       .map(ParseConfigLines.parseLines)
+      .catchAll(h =>
+        IO.fail(
+          List(ConfigValidation.ErrorReadingFile(filename, h.getMessage))))
 
-  private def readFile(filename: Path) = {
+  private def readFile(filename: Path): Task[List[String]] = {
     if (Files.exists(filename)) readFileThatExists(filename)
-    else IO.pure(List())
+    else IO(List())
   }
 
-  private def readFileThatExists(filename: Path) =
+  private def readFileThatExists(filename: Path): Task[List[String]] =
     for {
       lines <- IO(Files.lines(filename))
       list = lines.iterator.asScala.toList
+      //FIXME: use a bracket to close the file
       _ <- IO(lines.close())
     } yield list
 
diff --git a/core/src/main/scala/net/kemitix/thorp/core/PlanBuilder.scala b/core/src/main/scala/net/kemitix/thorp/core/PlanBuilder.scala
index 2e8c4aa..7f7796c 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/PlanBuilder.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/PlanBuilder.scala
@@ -1,11 +1,10 @@
 package net.kemitix.thorp.core
 
-import cats.data.{EitherT, NonEmptyChain}
-import cats.effect.IO
-import cats.implicits._
 import net.kemitix.thorp.core.Action.DoNothing
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.{HashService, StorageService}
+import zio.console._
+import zio.{Task, TaskR}
 
 trait PlanBuilder {
 
@@ -13,30 +12,29 @@ trait PlanBuilder {
       storageService: StorageService,
       hashService: HashService,
       configOptions: ConfigOptions
-  )(implicit l: Logger): EitherT[IO, List[String], SyncPlan] =
-    EitherT(ConfigurationBuilder.buildConfig(configOptions))
-      .leftMap(errorMessages)
-      .flatMap(config => useValidConfig(storageService, hashService)(config, l))
-
-  def errorMessages(errors: NonEmptyChain[ConfigValidation]): List[String] =
-    errors.map(cv => cv.errorMessage).toList
+  ): TaskR[Console, SyncPlan] =
+    ConfigurationBuilder
+      .buildConfig(configOptions)
+      .catchAll(errors => TaskR.fail(ConfigValidationException(errors)))
+      .flatMap(config => useValidConfig(storageService, hashService)(config))
 
   def useValidConfig(
       storageService: StorageService,
       hashService: HashService
-  )(implicit c: Config, l: Logger): EitherT[IO, List[String], SyncPlan] =
+  )(implicit c: Config): TaskR[Console, SyncPlan] = {
     for {
-      _       <- EitherT.liftF(SyncLogging.logRunStart(c.bucket, c.prefix, c.sources))
+      _       <- SyncLogging.logRunStart(c.bucket, c.prefix, c.sources)
       actions <- buildPlan(storageService, hashService)
     } yield actions
+  }
 
   private def buildPlan(
       storageService: StorageService,
       hashService: HashService
-  )(implicit c: Config, l: Logger) =
-    gatherMetadata(storageService, hashService)
-      .leftMap(List(_))
-      .map(assemblePlan)
+  )(implicit c: Config): TaskR[Console, SyncPlan] =
+    for {
+      metadata <- gatherMetadata(storageService, hashService)
+    } yield assemblePlan(c)(metadata)
 
   def assemblePlan(
       implicit c: Config): ((S3ObjectsData, LocalFiles)) => SyncPlan = {
@@ -91,21 +89,20 @@ trait PlanBuilder {
   private def gatherMetadata(
       storageService: StorageService,
       hashService: HashService
-  )(implicit l: Logger,
-    c: Config): EitherT[IO, String, (S3ObjectsData, LocalFiles)] =
+  )(implicit c: Config): TaskR[Console, (S3ObjectsData, LocalFiles)] =
     for {
       remoteData <- fetchRemoteData(storageService)
-      localData  <- EitherT.liftF(findLocalFiles(hashService))
+      localData  <- findLocalFiles(hashService)
     } yield (remoteData, localData)
 
   private def fetchRemoteData(
       storageService: StorageService
-  )(implicit c: Config, l: Logger) =
+  )(implicit c: Config): TaskR[Console, S3ObjectsData] =
     storageService.listObjects(c.bucket, c.prefix)
 
   private def findLocalFiles(
       hashService: HashService
-  )(implicit config: Config, l: Logger) =
+  )(implicit config: Config): TaskR[Console, LocalFiles] =
     for {
       _          <- SyncLogging.logFileScan
       localFiles <- findFiles(hashService)
@@ -113,19 +110,10 @@ trait PlanBuilder {
 
   private def findFiles(
       hashService: HashService
-  )(implicit c: Config, l: Logger) = {
-    val ioListLocalFiles = (for {
-      source <- c.sources.paths
-    } yield LocalFileStream.findFiles(source, hashService)).sequence
-    for {
-      listLocalFiles <- ioListLocalFiles
-      localFiles = listLocalFiles.foldRight(LocalFiles()) {
-        (acc, moreLocalFiles) =>
-          {
-            acc ++ moreLocalFiles
-          }
-      }
-    } yield localFiles
+  )(implicit c: Config): Task[LocalFiles] = {
+    Task
+      .foreach(c.sources.paths)(LocalFileStream.findFiles(_, hashService))
+      .map(_.foldLeft(LocalFiles())((acc, localFile) => acc ++ localFile))
   }
 
 }
diff --git a/core/src/main/scala/net/kemitix/thorp/core/SimpleHashService.scala b/core/src/main/scala/net/kemitix/thorp/core/SimpleHashService.scala
index bc54aa6..6991af6 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/SimpleHashService.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/SimpleHashService.scala
@@ -2,15 +2,15 @@ package net.kemitix.thorp.core
 
 import java.nio.file.Path
 
-import cats.effect.IO
-import net.kemitix.thorp.domain.{Logger, MD5Hash}
+import net.kemitix.thorp.domain.MD5Hash
 import net.kemitix.thorp.storage.api.HashService
+import zio.Task
 
 case class SimpleHashService() extends HashService {
 
   override def hashLocalObject(
       path: Path
-  )(implicit l: Logger): IO[Map[String, MD5Hash]] =
+  ): Task[Map[String, MD5Hash]] =
     for {
       md5 <- MD5HashGenerator.md5File(path)
     } yield Map("md5" -> md5)
diff --git a/core/src/main/scala/net/kemitix/thorp/core/SourceConfigLoader.scala b/core/src/main/scala/net/kemitix/thorp/core/SourceConfigLoader.scala
index 2b9daa6..2669802 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/SourceConfigLoader.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/SourceConfigLoader.scala
@@ -1,25 +1,26 @@
 package net.kemitix.thorp.core
 
-import cats.effect.IO
-import cats.implicits._
 import net.kemitix.thorp.domain.Sources
+import zio.IO
 
 trait SourceConfigLoader {
 
   val thorpConfigFileName = ".thorp.conf"
 
-  def loadSourceConfigs: Sources => IO[ConfigOptions] =
+  def loadSourceConfigs: Sources => IO[List[ConfigValidation], ConfigOptions] =
     sources => {
 
       val sourceConfigOptions =
-        ConfigOptions(sources.paths.map(ConfigOption.Source(_)))
+        ConfigOptions(sources.paths.map(ConfigOption.Source))
 
       val reduce: List[ConfigOptions] => ConfigOptions =
-        _.foldLeft(sourceConfigOptions) { (acc, co) => acc ++ co }
+        _.foldLeft(sourceConfigOptions) { (acc, co) =>
+          acc ++ co
+        }
 
-      sources.paths
-        .map(_.resolve(thorpConfigFileName))
-        .map(ParseConfigFile.parseFile).sequence
+      IO.foreach(sources.paths) { path =>
+          ParseConfigFile.parseFile(path.resolve(thorpConfigFileName))
+        }
         .map(reduce)
     }
 
diff --git a/core/src/main/scala/net/kemitix/thorp/core/SyncLogging.scala b/core/src/main/scala/net/kemitix/thorp/core/SyncLogging.scala
index d86c651..a4d6c32 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/SyncLogging.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/SyncLogging.scala
@@ -1,7 +1,5 @@
 package net.kemitix.thorp.core
 
-import cats.effect.IO
-import cats.implicits._
 import net.kemitix.thorp.domain.StorageQueueEvent.{
   CopyQueueEvent,
   DeleteQueueEvent,
@@ -9,6 +7,8 @@ import net.kemitix.thorp.domain.StorageQueueEvent.{
   UploadQueueEvent
 }
 import net.kemitix.thorp.domain._
+import zio.ZIO
+import zio.console._
 
 trait SyncLogging {
 
@@ -16,40 +16,44 @@ trait SyncLogging {
       bucket: Bucket,
       prefix: RemoteKey,
       sources: Sources
-  )(implicit logger: Logger): IO[Unit] = {
+  ): ZIO[Console, Nothing, Unit] = {
     val sourcesList = sources.paths.mkString(", ")
-    logger.info(
-      List(s"Bucket: ${bucket.name}",
-           s"Prefix: ${prefix.key}",
-           s"Source: $sourcesList")
-        .mkString(", "))
+    for {
+      _ <- putStrLn(
+        List(s"Bucket: ${bucket.name}",
+             s"Prefix: ${prefix.key}",
+             s"Source: $sourcesList")
+          .mkString(", "))
+    } yield ()
   }
 
-  def logFileScan(implicit c: Config, logger: Logger): IO[Unit] =
-    logger.info(s"Scanning local files: ${c.sources.paths.mkString(", ")}...")
+  def logFileScan(implicit c: Config): ZIO[Console, Nothing, Unit] =
+    putStrLn(s"Scanning local files: ${c.sources.paths.mkString(", ")}...")
 
   def logRunFinished(
       actions: Stream[StorageQueueEvent]
-  )(implicit logger: Logger): IO[Unit] = {
+  ): ZIO[Console, Nothing, Unit] = {
     val counters = actions.foldLeft(Counters())(countActivities)
     for {
-      _ <- logger.info(s"Uploaded ${counters.uploaded} files")
-      _ <- logger.info(s"Copied   ${counters.copied} files")
-      _ <- logger.info(s"Deleted  ${counters.deleted} files")
-      _ <- logger.info(s"Errors   ${counters.errors}")
+      _ <- putStrLn(s"Uploaded ${counters.uploaded} files")
+      _ <- putStrLn(s"Copied   ${counters.copied} files")
+      _ <- putStrLn(s"Deleted  ${counters.deleted} files")
+      _ <- putStrLn(s"Errors   ${counters.errors}")
       _ <- logErrors(actions)
     } yield ()
   }
 
   def logErrors(
       actions: Stream[StorageQueueEvent]
-  )(implicit logger: Logger): IO[Unit] =
-    for {
-      _ <- actions.map {
-        case ErrorQueueEvent(k, e) => logger.warn(s"${k.key}: ${e.getMessage}")
-        case _                     => IO.unit
-      }.sequence
-    } yield ()
+  ): ZIO[Console, Nothing, Unit] = {
+    ZIO.foldLeft(actions)(()) { (_, action) =>
+      action match {
+        case ErrorQueueEvent(k, e) =>
+          putStrLn(s"${k.key}: ${e.getMessage}")
+        case _ => ZIO.unit
+      }
+    }
+  }
 
   private def countActivities: (Counters, StorageQueueEvent) => Counters =
     (counters: Counters, s3Action: StorageQueueEvent) => {
diff --git a/core/src/main/scala/net/kemitix/thorp/core/ThorpArchive.scala b/core/src/main/scala/net/kemitix/thorp/core/ThorpArchive.scala
index 0382aff..297dce3 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/ThorpArchive.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/ThorpArchive.scala
@@ -1,7 +1,8 @@
 package net.kemitix.thorp.core
 
-import cats.effect.IO
-import net.kemitix.thorp.domain.{LocalFile, Logger, StorageQueueEvent}
+import net.kemitix.thorp.domain.{LocalFile, StorageQueueEvent}
+import zio.TaskR
+import zio.console._
 
 trait ThorpArchive {
 
@@ -9,13 +10,15 @@ trait ThorpArchive {
       index: Int,
       action: Action,
       totalBytesSoFar: Long
-  )(implicit l: Logger): Stream[IO[StorageQueueEvent]]
+  ): TaskR[Console, StorageQueueEvent]
 
   def logFileUploaded(
       localFile: LocalFile,
       batchMode: Boolean
-  )(implicit l: Logger): IO[Unit] =
-    if (batchMode) l.info(s"Uploaded: ${localFile.remoteKey.key}")
-    else IO.unit
+  ): TaskR[Console, Unit] =
+    for {
+      _ <- TaskR.when(batchMode)(
+        putStrLn(s"Uploaded: ${localFile.remoteKey.key}"))
+    } yield ()
 
 }
diff --git a/core/src/main/scala/net/kemitix/thorp/core/UnversionedMirrorArchive.scala b/core/src/main/scala/net/kemitix/thorp/core/UnversionedMirrorArchive.scala
index d353aa6..0a1dd60 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/UnversionedMirrorArchive.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/UnversionedMirrorArchive.scala
@@ -1,10 +1,11 @@
 package net.kemitix.thorp.core
 
-import cats.effect.IO
 import net.kemitix.thorp.core.Action.{DoNothing, ToCopy, ToDelete, ToUpload}
 import net.kemitix.thorp.domain.StorageQueueEvent.DoNothingQueueEvent
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.StorageService
+import zio.console.Console
+import zio.{Task, TaskR}
 
 case class UnversionedMirrorArchive(
     storageService: StorageService,
@@ -16,8 +17,8 @@ case class UnversionedMirrorArchive(
       index: Int,
       action: Action,
       totalBytesSoFar: Long
-  )(implicit l: Logger): Stream[IO[StorageQueueEvent]] =
-    Stream(action match {
+  ): TaskR[Console, StorageQueueEvent] =
+    action match {
       case ToUpload(bucket, localFile, _) =>
         for {
           event <- doUpload(index, totalBytesSoFar, bucket, localFile)
@@ -32,8 +33,8 @@ case class UnversionedMirrorArchive(
           event <- storageService.delete(bucket, remoteKey)
         } yield event
       case DoNothing(_, remoteKey, _) =>
-        IO.pure(DoNothingQueueEvent(remoteKey))
-    })
+        Task(DoNothingQueueEvent(remoteKey))
+    }
 
   private def doUpload(
       index: Int,
diff --git a/core/src/test/scala/net/kemitix/thorp/core/ConfigOptionTest.scala b/core/src/test/scala/net/kemitix/thorp/core/ConfigOptionTest.scala
index 997c845..73f5476 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/ConfigOptionTest.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/ConfigOptionTest.scala
@@ -2,6 +2,7 @@ package net.kemitix.thorp.core
 
 import net.kemitix.thorp.domain.Sources
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 class ConfigOptionTest extends FunSpec with TemporaryFolder {
 
@@ -27,6 +28,9 @@ class ConfigOptionTest extends FunSpec with TemporaryFolder {
   }
 
   private def invoke(configOptions: ConfigOptions) = {
-    ConfigurationBuilder.buildConfig(configOptions).unsafeRunSync
+    val runtime = new DefaultRuntime {}
+    runtime.unsafeRunSync {
+      ConfigurationBuilder.buildConfig(configOptions)
+    }.toEither
   }
 }
diff --git a/core/src/test/scala/net/kemitix/thorp/core/ConfigurationBuilderTest.scala b/core/src/test/scala/net/kemitix/thorp/core/ConfigurationBuilderTest.scala
index fb38050..df75c5f 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/ConfigurationBuilderTest.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/ConfigurationBuilderTest.scala
@@ -5,6 +5,7 @@ import java.nio.file.{Path, Paths}
 import net.kemitix.thorp.domain.Filter.{Exclude, Include}
 import net.kemitix.thorp.domain._
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 class ConfigurationBuilderTest extends FunSpec with TemporaryFolder {
 
@@ -23,8 +24,8 @@ class ConfigurationBuilderTest extends FunSpec with TemporaryFolder {
   describe("when no source") {
     it("should use the current (PWD) directory") {
       val expected = Right(Sources(List(pwd)))
-      val options = configOptions(coBucket)
-      val result = invoke(options).map(_.sources)
+      val options  = configOptions(coBucket)
+      val result   = invoke(options).map(_.sources)
       assertResult(expected)(result)
     }
   }
@@ -32,11 +33,12 @@ class ConfigurationBuilderTest extends FunSpec with TemporaryFolder {
     describe("with .thorp.conf") {
       describe("with settings") {
         withDirectory(source => {
-          val configFileName = createFile(source, thorpConfigFileName,
-            "bucket = a-bucket",
-            "prefix = a-prefix",
-            "include = an-inclusion",
-            "exclude = an-exclusion")
+          val configFileName = createFile(source,
+                                          thorpConfigFileName,
+                                          "bucket = a-bucket",
+                                          "prefix = a-prefix",
+                                          "include = an-inclusion",
+                                          "exclude = an-exclusion")
           val result = invoke(configOptions(ConfigOption.Source(source)))
           it("should have bucket") {
             val expected = Right(Bucket("a-bucket"))
@@ -47,7 +49,8 @@ class ConfigurationBuilderTest extends FunSpec with TemporaryFolder {
             assertResult(expected)(result.map(_.prefix))
           }
           it("should have filters") {
-            val expected = Right(List(Exclude("an-exclusion"), Include("an-inclusion")))
+            val expected =
+              Right(List(Exclude("an-exclusion"), Include("an-inclusion")))
             assertResult(expected)(result.map(_.filters))
           }
         })
@@ -120,9 +123,9 @@ class ConfigurationBuilderTest extends FunSpec with TemporaryFolder {
             // should have prefix from current only
             val expectedPrefixes = Right(RemoteKey("current-prefix"))
             // should have filters from both sources
-            val expectedFilters = Right(List(
-              Filter.Exclude("current-exclude"),
-              Filter.Include("current-include")))
+            val expectedFilters = Right(
+              List(Filter.Exclude("current-exclude"),
+                   Filter.Include("current-include")))
             val options = configOptions(ConfigOption.Source(currentSource))
             val result  = invoke(options)
             assertResult(expectedSources)(result.map(_.sources))
@@ -135,7 +138,8 @@ class ConfigurationBuilderTest extends FunSpec with TemporaryFolder {
     }
   }
 
-  describe("when source has thorp.config source to another source that does the same") {
+  describe(
+    "when source has thorp.config source to another source that does the same") {
     it("should only include first two sources") {
       withDirectory(currentSource => {
         withDirectory(parentSource => {
@@ -143,11 +147,12 @@ class ConfigurationBuilderTest extends FunSpec with TemporaryFolder {
                     thorpConfigFileName,
                     s"source = $parentSource")
           withDirectory(grandParentSource => {
-            writeFile(parentSource, thorpConfigFileName, s"source = $grandParentSource")
+            writeFile(parentSource,
+                      thorpConfigFileName,
+                      s"source = $grandParentSource")
             val expected = Right(List(currentSource, parentSource))
-            val options = configOptions(
-              ConfigOption.Source(currentSource),
-              coBucket)
+            val options =
+              configOptions(ConfigOption.Source(currentSource), coBucket)
             val result = invoke(options).map(_.sources.paths)
             assertResult(expected)(result)
           })
@@ -156,7 +161,11 @@ class ConfigurationBuilderTest extends FunSpec with TemporaryFolder {
     }
   }
 
-  private def invoke(configOptions: ConfigOptions) =
-    ConfigurationBuilder.buildConfig(configOptions).unsafeRunSync
+  private def invoke(configOptions: ConfigOptions) = {
+    val runtime = new DefaultRuntime {}
+    runtime.unsafeRunSync {
+      ConfigurationBuilder.buildConfig(configOptions)
+    }.toEither
+  }
 
 }
diff --git a/core/src/test/scala/net/kemitix/thorp/core/DummyHashService.scala b/core/src/test/scala/net/kemitix/thorp/core/DummyHashService.scala
index 2663b89..31b7941 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/DummyHashService.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/DummyHashService.scala
@@ -2,15 +2,14 @@ package net.kemitix.thorp.core
 
 import java.nio.file.Path
 
-import cats.effect.IO
-import net.kemitix.thorp.domain.{Logger, MD5Hash}
+import net.kemitix.thorp.domain.MD5Hash
 import net.kemitix.thorp.storage.api.HashService
+import zio.Task
 
 case class DummyHashService(hashes: Map[Path, Map[String, MD5Hash]])
     extends HashService {
 
-  override def hashLocalObject(path: Path)(
-      implicit l: Logger): IO[Map[String, MD5Hash]] =
-    IO.pure(hashes(path))
+  override def hashLocalObject(path: Path): Task[Map[String, MD5Hash]] =
+    Task(hashes(path))
 
 }
diff --git a/core/src/test/scala/net/kemitix/thorp/core/DummyLogger.scala b/core/src/test/scala/net/kemitix/thorp/core/DummyLogger.scala
deleted file mode 100644
index 4b2329c..0000000
--- a/core/src/test/scala/net/kemitix/thorp/core/DummyLogger.scala
+++ /dev/null
@@ -1,18 +0,0 @@
-package net.kemitix.thorp.core
-
-import cats.effect.IO
-import net.kemitix.thorp.domain.Logger
-
-class DummyLogger extends Logger {
-
-  override def debug(message: => String): IO[Unit] = IO.unit
-
-  override def info(message: => String): IO[Unit] = IO.unit
-
-  override def warn(message: String): IO[Unit] = IO.unit
-
-  override def error(message: String): IO[Unit] = IO.unit
-
-  override def withDebug(debug: Boolean): Logger = this
-
-}
diff --git a/core/src/test/scala/net/kemitix/thorp/core/DummyStorageService.scala b/core/src/test/scala/net/kemitix/thorp/core/DummyStorageService.scala
index b44a49c..79b313b 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/DummyStorageService.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/DummyStorageService.scala
@@ -2,39 +2,39 @@ package net.kemitix.thorp.core
 
 import java.io.File
 
-import cats.data.EitherT
-import cats.effect.IO
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.StorageService
+import zio.console.Console
+import zio.{Task, TaskR}
 
 case class DummyStorageService(s3ObjectData: S3ObjectsData,
                                uploadFiles: Map[File, (RemoteKey, MD5Hash)])
     extends StorageService {
 
-  override def shutdown: IO[StorageQueueEvent] =
-    IO.pure(StorageQueueEvent.ShutdownQueueEvent())
+  override def shutdown: Task[StorageQueueEvent] =
+    Task(StorageQueueEvent.ShutdownQueueEvent())
 
-  override def listObjects(bucket: Bucket, prefix: RemoteKey)(
-      implicit l: Logger): EitherT[IO, String, S3ObjectsData] =
-    EitherT.liftF(IO.pure(s3ObjectData))
+  override def listObjects(bucket: Bucket,
+                           prefix: RemoteKey): TaskR[Console, S3ObjectsData] =
+    TaskR(s3ObjectData)
 
   override def upload(localFile: LocalFile,
                       bucket: Bucket,
                       batchMode: Boolean,
                       uploadEventListener: UploadEventListener,
-                      tryCount: Int): IO[StorageQueueEvent] = {
+                      tryCount: Int): Task[StorageQueueEvent] = {
     val (remoteKey, md5Hash) = uploadFiles(localFile.file)
-    IO.pure(StorageQueueEvent.UploadQueueEvent(remoteKey, md5Hash))
+    Task(StorageQueueEvent.UploadQueueEvent(remoteKey, md5Hash))
   }
 
   override def copy(bucket: Bucket,
                     sourceKey: RemoteKey,
                     hash: MD5Hash,
-                    targetKey: RemoteKey): IO[StorageQueueEvent] =
-    IO.pure(StorageQueueEvent.CopyQueueEvent(targetKey))
+                    targetKey: RemoteKey): Task[StorageQueueEvent] =
+    Task(StorageQueueEvent.CopyQueueEvent(targetKey))
 
   override def delete(bucket: Bucket,
-                      remoteKey: RemoteKey): IO[StorageQueueEvent] =
-    IO.pure(StorageQueueEvent.DeleteQueueEvent(remoteKey))
+                      remoteKey: RemoteKey): Task[StorageQueueEvent] =
+    Task(StorageQueueEvent.DeleteQueueEvent(remoteKey))
 
 }
diff --git a/core/src/test/scala/net/kemitix/thorp/core/LocalFileStreamSuite.scala b/core/src/test/scala/net/kemitix/thorp/core/LocalFileStreamSuite.scala
index b8f0a34..9388a01 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/LocalFileStreamSuite.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/LocalFileStreamSuite.scala
@@ -5,6 +5,7 @@ import java.nio.file.Paths
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.HashService
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 class LocalFileStreamSuite extends FunSpec {
 
@@ -21,28 +22,34 @@ class LocalFileStreamSuite extends FunSpec {
 
   implicit private val config: Config = Config(
     sources = Sources(List(sourcePath)))
-  implicit private val logger: Logger = new DummyLogger
 
   describe("findFiles") {
     it("should find all files") {
-      val result: Set[String] =
-        invoke.localFiles.toSet
-          .map { x: LocalFile =>
-            x.relative.toString
-          }
-      assertResult(Set("subdir/leaf-file", "root-file"))(result)
+      val expected = Right(Set("subdir/leaf-file", "root-file"))
+      val result =
+        invoke()
+          .map(_.localFiles)
+          .map(localFiles => localFiles.map(_.relative.toString))
+          .map(_.toSet)
+      assertResult(expected)(result)
     }
     it("should count all files") {
-      val result = invoke.count
-      assertResult(2)(result)
+      val expected = Right(2)
+      val result   = invoke().map(_.count)
+      assertResult(expected)(result)
     }
     it("should sum the size of all files") {
-      val result = invoke.totalSizeBytes
-      assertResult(113)(result)
+      val expected = Right(113)
+      val result   = invoke().map(_.totalSizeBytes)
+      assertResult(expected)(result)
     }
   }
 
-  private def invoke =
-    LocalFileStream.findFiles(sourcePath, hashService).unsafeRunSync
+  private def invoke() = {
+    val runtime = new DefaultRuntime {}
+    runtime.unsafeRunSync {
+      LocalFileStream.findFiles(sourcePath, hashService)
+    }.toEither
+  }
 
 }
diff --git a/core/src/test/scala/net/kemitix/thorp/core/MD5HashGeneratorTest.scala b/core/src/test/scala/net/kemitix/thorp/core/MD5HashGeneratorTest.scala
index 1d43637..e6a091e 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/MD5HashGeneratorTest.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/MD5HashGeneratorTest.scala
@@ -1,50 +1,69 @@
 package net.kemitix.thorp.core
 
-import net.kemitix.thorp.domain.MD5HashData.Root
+import java.nio.file.Path
+
+import net.kemitix.thorp.domain.MD5HashData.{BigFile, Root}
 import net.kemitix.thorp.domain._
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 class MD5HashGeneratorTest extends FunSpec {
 
+  private val runtime = new DefaultRuntime {}
+
   private val source     = Resource(this, "upload")
   private val sourcePath = source.toPath
   private val prefix     = RemoteKey("prefix")
   implicit private val config: Config =
     Config(Bucket("bucket"), prefix, sources = Sources(List(sourcePath)))
-  implicit private val logger: Logger = new DummyLogger
 
-  describe("read a small file (smaller than buffer)") {
-    val path = Resource(this, "upload/root-file").toPath
-    it("should generate the correct hash") {
-      val result = MD5HashGenerator.md5File(path).unsafeRunSync
-      assertResult(Root.hash)(result)
+  describe("md5File()") {
+    describe("read a small file (smaller than buffer)") {
+      val path = Resource(this, "upload/root-file").toPath
+      it("should generate the correct hash") {
+        val expected = Right(Root.hash)
+        val result   = invoke(path)
+        assertResult(expected)(result)
+      }
+    }
+
+    describe("read a large file (bigger than buffer)") {
+      val path = Resource(this, "big-file").toPath
+      it("should generate the correct hash") {
+        val expected = Right(BigFile.hash)
+        val result   = invoke(path)
+        assertResult(expected)(result)
+      }
+    }
+
+    def invoke(path: Path) = {
+      runtime.unsafeRunSync {
+        MD5HashGenerator.md5File(path)
+      }.toEither
     }
   }
-  describe("read a large file (bigger than buffer)") {
-    val path = Resource(this, "big-file").toPath
-    it("should generate the correct hash") {
-      val expected = MD5HashData.BigFile.hash
-      val result   = MD5HashGenerator.md5File(path).unsafeRunSync
-      assertResult(expected)(result)
+
+  describe("md5FileChunk") {
+    describe("read chunks of file") {
+      val path = Resource(this, "big-file").toPath
+      it("should generate the correct hash for first chunk of the file") {
+        val part1    = BigFile.Part1
+        val expected = Right(part1.hash.hash)
+        val result   = invoke(path, part1.offset, part1.size).map(_.hash)
+        assertResult(expected)(result)
+      }
+      it("should generate the correct hash for second chunk of the file") {
+        val part2    = BigFile.Part2
+        val expected = Right(part2.hash.hash)
+        val result   = invoke(path, part2.offset, part2.size).map(_.hash)
+        assertResult(expected)(result)
+      }
     }
-  }
-  describe("read chunks of file") {
-    val path = Resource(this, "big-file").toPath
-    it("should generate the correct hash for first chunk of the file") {
-      val part1    = MD5HashData.BigFile.Part1
-      val expected = part1.hash
-      val result = MD5HashGenerator
-        .md5FileChunk(path, part1.offset, part1.size)
-        .unsafeRunSync
-      assertResult(expected)(result)
-    }
-    it("should generate the correcy hash for second chunk of the file") {
-      val part2    = MD5HashData.BigFile.Part2
-      val expected = part2.hash
-      val result = MD5HashGenerator
-        .md5FileChunk(path, part2.offset, part2.size)
-        .unsafeRunSync
-      assertResult(expected)(result)
+
+    def invoke(path: Path, offset: Long, size: Long) = {
+      runtime.unsafeRunSync {
+        MD5HashGenerator.md5FileChunk(path, offset, size)
+      }.toEither
     }
   }
 
diff --git a/core/src/test/scala/net/kemitix/thorp/core/ParseConfigFileTest.scala b/core/src/test/scala/net/kemitix/thorp/core/ParseConfigFileTest.scala
index e78d10b..e3cb0df 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/ParseConfigFileTest.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/ParseConfigFileTest.scala
@@ -3,13 +3,11 @@ package net.kemitix.thorp.core
 import java.nio.file.{Path, Paths}
 
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 class ParseConfigFileTest extends FunSpec {
 
-  private val empty = ConfigOptions()
-
-  private def invoke(filename: Path) =
-    ParseConfigFile.parseFile(filename).unsafeRunSync
+  private val empty = Right(ConfigOptions())
 
   describe("parse a missing file") {
     val filename = Paths.get("/path/to/missing/file")
@@ -31,11 +29,18 @@ class ParseConfigFileTest extends FunSpec {
   }
   describe("parse a file with properties") {
     val filename = Resource(this, "simple-config").toPath
-    val expected = ConfigOptions(
-      List(ConfigOption.Source(Paths.get("/path/to/source")),
-           ConfigOption.Bucket("bucket-name")))
+    val expected = Right(
+      ConfigOptions(List(ConfigOption.Source(Paths.get("/path/to/source")),
+                         ConfigOption.Bucket("bucket-name"))))
     it("should return some options") {
       assertResult(expected)(invoke(filename))
     }
   }
+
+  private def invoke(filename: Path) = {
+    val runtime = new DefaultRuntime {}
+    runtime.unsafeRunSync {
+      ParseConfigFile.parseFile(filename)
+    }.toEither
+  }
 }
diff --git a/core/src/test/scala/net/kemitix/thorp/core/PlanBuilderTest.scala b/core/src/test/scala/net/kemitix/thorp/core/PlanBuilderTest.scala
index 724deba..05fa48c 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/PlanBuilderTest.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/PlanBuilderTest.scala
@@ -7,12 +7,15 @@ import net.kemitix.thorp.core.Action.{DoNothing, ToCopy, ToDelete, ToUpload}
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.{HashService, StorageService}
 import org.scalatest.FreeSpec
+import zio.DefaultRuntime
 
 class PlanBuilderTest extends FreeSpec with TemporaryFolder {
-  val lastModified: LastModified      = LastModified()
-  private val planBuilder             = new PlanBuilder {}
-  private implicit val logger: Logger = new DummyLogger
-  private val emptyS3ObjectData       = S3ObjectsData()
+
+  private val runtime = new DefaultRuntime {}
+
+  private val lastModified: LastModified = LastModified()
+  private val planBuilder                = new PlanBuilder {}
+  private val emptyS3ObjectData          = S3ObjectsData()
 
   "create a plan" - {
 
@@ -426,7 +429,14 @@ class PlanBuilderTest extends FreeSpec with TemporaryFolder {
     }
 
     def md5Hash(file: File) = {
-      hashService.hashLocalObject(file.toPath).unsafeRunSync()("md5")
+      runtime
+        .unsafeRunSync {
+          hashService.hashLocalObject(file.toPath).map(_.get("md5"))
+        }
+        .toEither
+        .toOption
+        .flatten
+        .getOrElse(MD5Hash("invalid md5 hash in test"))
     }
 
   }
@@ -450,14 +460,17 @@ class PlanBuilderTest extends FreeSpec with TemporaryFolder {
   private def configOptions(configOptions: ConfigOption*): ConfigOptions =
     ConfigOptions(List(configOptions: _*))
 
-  private def invoke(storageService: StorageService,
-                     hashService: HashService,
-                     configOptions: ConfigOptions)
-    : Either[List[String], List[(String, String, String, String, String)]] =
-    planBuilder
-      .createPlan(storageService, hashService, configOptions)
-      .value
-      .unsafeRunSync()
+  private def invoke(
+      storageService: StorageService,
+      hashService: HashService,
+      configOptions: ConfigOptions
+  ): Either[Any, List[(String, String, String, String, String)]] =
+    runtime
+      .unsafeRunSync {
+        planBuilder
+          .createPlan(storageService, hashService, configOptions)
+      }
+      .toEither
       .map(_.actions.toList.map({
         case ToUpload(_, lf, _) =>
           ("upload",
diff --git a/core/src/test/scala/net/kemitix/thorp/core/SyncSuite.scala b/core/src/test/scala/net/kemitix/thorp/core/SyncSuite.scala
index c1c0ffc..dce6d89 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/SyncSuite.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/SyncSuite.scala
@@ -4,8 +4,6 @@ import java.io.File
 import java.nio.file.Paths
 import java.time.Instant
 
-import cats.data.EitherT
-import cats.effect.IO
 import net.kemitix.thorp.core.Action.{ToCopy, ToDelete, ToUpload}
 import net.kemitix.thorp.domain.MD5HashData.{Leaf, Root}
 import net.kemitix.thorp.domain.StorageQueueEvent.{
@@ -17,8 +15,13 @@ import net.kemitix.thorp.domain.StorageQueueEvent.{
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.{HashService, StorageService}
 import org.scalatest.FunSpec
+import zio.console.Console
+import zio.{DefaultRuntime, Task, TaskR}
 
 class SyncSuite extends FunSpec {
+
+  private val runtime = new DefaultRuntime {}
+
   private val testBucket = Bucket("bucket")
   private val source     = Resource(this, "upload")
   private val sourcePath = source.toPath
@@ -30,7 +33,6 @@ class SyncSuite extends FunSpec {
                       md5HashMap(Root.hash),
                       sourcePath,
                       _ => rootRemoteKey)
-  implicit private val logger: Logger = new DummyLogger
   private val leafFile: LocalFile =
     LocalFile.resolve("subdir/leaf-file",
                       md5HashMap(Leaf.hash),
@@ -58,24 +60,6 @@ class SyncSuite extends FunSpec {
                        localFile: LocalFile): (String, String, File) =
     (bucket.name, remoteKey.key, localFile.file)
 
-  def invokeSubjectForActions(
-      storageService: StorageService,
-      hashService: HashService,
-      configOptions: ConfigOptions): Either[List[String], Stream[Action]] = {
-    invokeSubject(storageService, hashService, configOptions)
-      .map(_.actions)
-  }
-
-  def invokeSubject(
-      storageService: StorageService,
-      hashService: HashService,
-      configOptions: ConfigOptions): Either[List[String], SyncPlan] = {
-    PlanBuilder
-      .createPlan(storageService, hashService, configOptions)
-      .value
-      .unsafeRunSync
-  }
-
   private def md5HashMap(md5Hash: MD5Hash): Map[String, MD5Hash] =
     Map("md5" -> md5Hash)
 
@@ -211,28 +195,45 @@ class SyncSuite extends FunSpec {
                                 s3ObjectsData: S3ObjectsData)
       extends StorageService {
 
-    override def listObjects(bucket: Bucket, prefix: RemoteKey)(
-        implicit l: Logger): EitherT[IO, String, S3ObjectsData] =
-      EitherT.liftF(IO.pure(s3ObjectsData))
+    override def listObjects(bucket: Bucket,
+                             prefix: RemoteKey): TaskR[Console, S3ObjectsData] =
+      TaskR(s3ObjectsData)
 
     override def upload(localFile: LocalFile,
                         bucket: Bucket,
                         batchMode: Boolean,
                         uploadEventListener: UploadEventListener,
-                        tryCount: Int): IO[UploadQueueEvent] =
-      IO.pure(UploadQueueEvent(localFile.remoteKey, localFile.hashes("md5")))
+                        tryCount: Int): Task[UploadQueueEvent] =
+      Task(UploadQueueEvent(localFile.remoteKey, localFile.hashes("md5")))
 
     override def copy(bucket: Bucket,
                       sourceKey: RemoteKey,
                       hashes: MD5Hash,
-                      targetKey: RemoteKey): IO[CopyQueueEvent] =
-      IO.pure(CopyQueueEvent(targetKey))
+                      targetKey: RemoteKey): Task[CopyQueueEvent] =
+      Task(CopyQueueEvent(targetKey))
 
     override def delete(bucket: Bucket,
-                        remoteKey: RemoteKey): IO[DeleteQueueEvent] =
-      IO.pure(DeleteQueueEvent(remoteKey))
+                        remoteKey: RemoteKey): Task[DeleteQueueEvent] =
+      Task(DeleteQueueEvent(remoteKey))
 
-    override def shutdown: IO[StorageQueueEvent] =
-      IO.pure(ShutdownQueueEvent())
+    override def shutdown: Task[StorageQueueEvent] =
+      Task(ShutdownQueueEvent())
+  }
+
+  def invokeSubjectForActions(
+      storageService: StorageService,
+      hashService: HashService,
+      configOptions: ConfigOptions): Either[Any, Stream[Action]] = {
+    invoke(storageService, hashService, configOptions)
+      .map(_.actions)
+  }
+
+  def invoke(storageService: StorageService,
+             hashService: HashService,
+             configOptions: ConfigOptions): Either[Any, SyncPlan] = {
+    runtime.unsafeRunSync {
+      PlanBuilder
+        .createPlan(storageService, hashService, configOptions)
+    }.toEither
   }
 }
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/Logger.scala b/domain/src/main/scala/net/kemitix/thorp/domain/Logger.scala
index 6e13b78..8862d74 100644
--- a/domain/src/main/scala/net/kemitix/thorp/domain/Logger.scala
+++ b/domain/src/main/scala/net/kemitix/thorp/domain/Logger.scala
@@ -1,7 +1,5 @@
 package net.kemitix.thorp.domain
 
-import cats.effect.IO
-
 trait Logger {
 
   // returns an instance of Logger with debug set as indicated
@@ -9,9 +7,9 @@ trait Logger {
   // it returns itself, unmodified
   def withDebug(debug: Boolean): Logger
 
-  def debug(message: => String): IO[Unit]
-  def info(message: => String): IO[Unit]
-  def warn(message: String): IO[Unit]
-  def error(message: String): IO[Unit]
+  def debug(message: => String): Unit
+  def info(message: => String): Unit
+  def warn(message: String): Unit
+  def error(message: String): Unit
 
 }
diff --git a/storage-api/src/main/scala/net/kemitix/thorp/storage/api/HashService.scala b/storage-api/src/main/scala/net/kemitix/thorp/storage/api/HashService.scala
index a7325b0..6b2c022 100644
--- a/storage-api/src/main/scala/net/kemitix/thorp/storage/api/HashService.scala
+++ b/storage-api/src/main/scala/net/kemitix/thorp/storage/api/HashService.scala
@@ -2,14 +2,14 @@ package net.kemitix.thorp.storage.api
 
 import java.nio.file.Path
 
-import cats.effect.IO
-import net.kemitix.thorp.domain.{Logger, MD5Hash}
+import net.kemitix.thorp.domain.MD5Hash
+import zio.Task
 
 /**
   * Creates one, or more, hashes for local objects.
   */
 trait HashService {
 
-  def hashLocalObject(path: Path)(implicit l: Logger): IO[Map[String, MD5Hash]]
+  def hashLocalObject(path: Path): Task[Map[String, MD5Hash]]
 
 }
diff --git a/storage-api/src/main/scala/net/kemitix/thorp/storage/api/StorageService.scala b/storage-api/src/main/scala/net/kemitix/thorp/storage/api/StorageService.scala
index 92d5b2e..0e38d45 100644
--- a/storage-api/src/main/scala/net/kemitix/thorp/storage/api/StorageService.scala
+++ b/storage-api/src/main/scala/net/kemitix/thorp/storage/api/StorageService.scala
@@ -1,17 +1,17 @@
 package net.kemitix.thorp.storage.api
 
-import cats.data.EitherT
-import cats.effect.IO
 import net.kemitix.thorp.domain._
+import zio.console.Console
+import zio.{Task, TaskR}
 
 trait StorageService {
 
-  def shutdown: IO[StorageQueueEvent]
+  def shutdown: Task[StorageQueueEvent]
 
   def listObjects(
       bucket: Bucket,
       prefix: RemoteKey
-  )(implicit l: Logger): EitherT[IO, String, S3ObjectsData]
+  ): TaskR[Console, S3ObjectsData]
 
   def upload(
       localFile: LocalFile,
@@ -19,18 +19,18 @@ trait StorageService {
       batchMode: Boolean,
       uploadEventListener: UploadEventListener,
       tryCount: Int
-  ): IO[StorageQueueEvent]
+  ): Task[StorageQueueEvent]
 
   def copy(
       bucket: Bucket,
       sourceKey: RemoteKey,
       hash: MD5Hash,
       targetKey: RemoteKey
-  ): IO[StorageQueueEvent]
+  ): Task[StorageQueueEvent]
 
   def delete(
       bucket: Bucket,
       remoteKey: RemoteKey
-  ): IO[StorageQueueEvent]
+  ): Task[StorageQueueEvent]
 
 }
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Copier.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Copier.scala
index 55bef98..61f8b51 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Copier.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Copier.scala
@@ -1,10 +1,10 @@
 package net.kemitix.thorp.storage.aws
 
-import cats.effect.IO
 import com.amazonaws.services.s3.AmazonS3
 import com.amazonaws.services.s3.model.CopyObjectRequest
 import net.kemitix.thorp.domain.StorageQueueEvent.CopyQueueEvent
 import net.kemitix.thorp.domain._
+import zio.Task
 
 class Copier(amazonS3: AmazonS3) {
 
@@ -13,7 +13,7 @@ class Copier(amazonS3: AmazonS3) {
       sourceKey: RemoteKey,
       hash: MD5Hash,
       targetKey: RemoteKey
-  ): IO[StorageQueueEvent] =
+  ): Task[StorageQueueEvent] =
     for {
       _ <- copyObject(bucket, sourceKey, hash, targetKey)
     } yield CopyQueueEvent(targetKey)
@@ -31,7 +31,7 @@ class Copier(amazonS3: AmazonS3) {
         bucket.name,
         targetKey.key
       ).withMatchingETagConstraint(hash.hash)
-    IO(amazonS3.copyObject(request))
+    Task(amazonS3.copyObject(request))
   }
 
 }
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Deleter.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Deleter.scala
index 05ff619..8a1f84e 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Deleter.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Deleter.scala
@@ -1,17 +1,17 @@
 package net.kemitix.thorp.storage.aws
 
-import cats.effect.IO
 import com.amazonaws.services.s3.AmazonS3
 import com.amazonaws.services.s3.model.DeleteObjectRequest
 import net.kemitix.thorp.domain.StorageQueueEvent.DeleteQueueEvent
 import net.kemitix.thorp.domain.{Bucket, RemoteKey, StorageQueueEvent}
+import zio.Task
 
 class Deleter(amazonS3: AmazonS3) {
 
   def delete(
       bucket: Bucket,
       remoteKey: RemoteKey
-  ): IO[StorageQueueEvent] =
+  ): Task[StorageQueueEvent] =
     for {
       _ <- deleteObject(bucket, remoteKey)
     } yield DeleteQueueEvent(remoteKey)
@@ -21,7 +21,7 @@ class Deleter(amazonS3: AmazonS3) {
       remoteKey: RemoteKey
   ) = {
     val request = new DeleteObjectRequest(bucket.name, remoteKey.key)
-    IO(amazonS3.deleteObject(request))
+    Task(amazonS3.deleteObject(request))
   }
 
 }
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/ETagGenerator.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/ETagGenerator.scala
index e0a68a3..69f9fe9 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/ETagGenerator.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/ETagGenerator.scala
@@ -2,25 +2,25 @@ package net.kemitix.thorp.storage.aws
 
 import java.nio.file.Path
 
-import cats.effect.IO
-import cats.implicits._
 import com.amazonaws.services.s3.model.PutObjectRequest
 import com.amazonaws.services.s3.transfer.TransferManagerConfiguration
 import com.amazonaws.services.s3.transfer.internal.TransferManagerUtils
 import net.kemitix.thorp.core.MD5HashGenerator
-import net.kemitix.thorp.domain.{Logger, MD5Hash}
+import net.kemitix.thorp.domain.MD5Hash
+import zio.Task
 
 trait ETagGenerator {
 
   def eTag(
       path: Path
-  )(implicit l: Logger): IO[String] = {
+  ): Task[String] = {
     val partSize = calculatePartSize(path)
     val parts    = numParts(path.toFile.length, partSize)
-    partsIndex(parts)
-      .map(digestChunk(path, partSize))
-      .sequence
-      .map(concatenateDigests)
+    Task
+      .foreach(partsIndex(parts)) { chunkNumber =>
+        digestChunk(path, partSize)(chunkNumber)
+      }
+      .map(parts => concatenateDigests(parts))
       .map(MD5HashGenerator.hex)
       .map(hash => s"$hash-$parts")
   }
@@ -53,14 +53,14 @@ trait ETagGenerator {
       chunkSize: Long
   )(
       chunkNumber: Long
-  )(implicit l: Logger): IO[Array[Byte]] =
+  ): Task[Array[Byte]] =
     hashChunk(path, chunkNumber, chunkSize).map(_.digest)
 
   def hashChunk(
       path: Path,
       chunkNumber: Long,
       chunkSize: Long
-  )(implicit l: Logger): IO[MD5Hash] =
+  ): Task[MD5Hash] =
     MD5HashGenerator.md5FileChunk(path, chunkNumber * chunkSize, chunkSize)
 
   def offsets(
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Lister.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Lister.scala
index f508d7e..772a5c2 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Lister.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Lister.scala
@@ -1,17 +1,15 @@
 package net.kemitix.thorp.storage.aws
 
-import cats.data.EitherT
-import cats.effect.IO
-import cats.implicits._
 import com.amazonaws.services.s3.AmazonS3
 import com.amazonaws.services.s3.model.{ListObjectsV2Request, S3ObjectSummary}
 import net.kemitix.thorp.domain
-import net.kemitix.thorp.domain.{Bucket, Logger, RemoteKey, S3ObjectsData}
+import net.kemitix.thorp.domain.{Bucket, RemoteKey, S3ObjectsData}
 import net.kemitix.thorp.storage.aws.S3ObjectsByHash.byHash
 import net.kemitix.thorp.storage.aws.S3ObjectsByKey.byKey
+import zio.console.Console
+import zio.{IO, Task, TaskR, ZIO}
 
 import scala.collection.JavaConverters._
-import scala.util.Try
 
 class Lister(amazonS3: AmazonS3) {
 
@@ -21,7 +19,7 @@ class Lister(amazonS3: AmazonS3) {
   def listObjects(
       bucket: Bucket,
       prefix: RemoteKey
-  )(implicit l: Logger): EitherT[IO, String, S3ObjectsData] = {
+  ): TaskR[Console, S3ObjectsData] = {
 
     val requestMore = (token: Token) =>
       new ListObjectsV2Request()
@@ -29,26 +27,23 @@ class Lister(amazonS3: AmazonS3) {
         .withPrefix(prefix.key)
         .withContinuationToken(token)
 
-    def fetchBatch: ListObjectsV2Request => EitherT[IO, String, Batch] =
+    def fetchBatch: ListObjectsV2Request => TaskR[Console, Batch] =
       request =>
-        EitherT {
-          for {
-            _     <- ListerLogger.logFetchBatch
-            batch <- tryFetchBatch(request)
-          } yield batch
-      }
+        for {
+          _     <- ListerLogger.logFetchBatch
+          batch <- tryFetchBatch(request)
+        } yield batch
 
     def fetchMore(
         more: Option[Token]
-    ): EitherT[IO, String, Stream[S3ObjectSummary]] = {
+    ): TaskR[Console, Stream[S3ObjectSummary]] = {
       more match {
-        case None        => EitherT.right(IO.pure(Stream.empty))
+        case None        => ZIO.succeed(Stream.empty)
         case Some(token) => fetch(requestMore(token))
       }
     }
 
-    def fetch
-      : ListObjectsV2Request => EitherT[IO, String, Stream[S3ObjectSummary]] =
+    def fetch: ListObjectsV2Request => TaskR[Console, Stream[S3ObjectSummary]] =
       request => {
         for {
           batch <- fetchBatch(request)
@@ -67,17 +62,12 @@ class Lister(amazonS3: AmazonS3) {
 
   private def tryFetchBatch(
       request: ListObjectsV2Request
-  ): IO[Either[String, (Stream[S3ObjectSummary], Option[Token])]] = {
-    IO {
-      Try(amazonS3.listObjectsV2(request))
-        .map { result =>
-          val more: Option[Token] =
-            if (result.isTruncated) Some(result.getNextContinuationToken)
-            else None
-          (result.getObjectSummaries.asScala.toStream, more)
-        }
-        .toEither
-        .leftMap(e => e.getMessage)
-    }
-  }
+  ): Task[(Stream[S3ObjectSummary], Option[Token])] =
+    IO(amazonS3.listObjectsV2(request))
+      .map { result =>
+        val more: Option[Token] =
+          if (result.isTruncated) Some(result.getNextContinuationToken)
+          else None
+        (result.getObjectSummaries.asScala.toStream, more)
+      }
 }
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/ListerLogger.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/ListerLogger.scala
index c07548e..1bd49d5 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/ListerLogger.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/ListerLogger.scala
@@ -1,10 +1,10 @@
 package net.kemitix.thorp.storage.aws
 
-import cats.effect.IO
-import net.kemitix.thorp.domain.Logger
+import zio.TaskR
+import zio.console._
 
 trait ListerLogger {
-  def logFetchBatch(implicit l: Logger): IO[Unit] =
-    l.info("Fetching remote summaries...")
+  def logFetchBatch: TaskR[Console, Unit] =
+    putStrLn("Fetching remote summaries...")
 }
 object ListerLogger extends ListerLogger
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/S3HashService.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/S3HashService.scala
index 495fb7b..644ca33 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/S3HashService.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/S3HashService.scala
@@ -2,10 +2,10 @@ package net.kemitix.thorp.storage.aws
 
 import java.nio.file.Path
 
-import cats.effect.IO
 import net.kemitix.thorp.core.MD5HashGenerator
-import net.kemitix.thorp.domain.{Logger, MD5Hash}
+import net.kemitix.thorp.domain.MD5Hash
 import net.kemitix.thorp.storage.api.HashService
+import zio.Task
 
 trait S3HashService extends HashService {
 
@@ -17,7 +17,7 @@ trait S3HashService extends HashService {
     */
   override def hashLocalObject(
       path: Path
-  )(implicit l: Logger): IO[Map[String, MD5Hash]] =
+  ): Task[Map[String, MD5Hash]] =
     for {
       md5  <- MD5HashGenerator.md5File(path)
       etag <- ETagGenerator.eTag(path).map(MD5Hash(_))
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/S3StorageService.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/S3StorageService.scala
index d6e57d7..bdfa15d 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/S3StorageService.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/S3StorageService.scala
@@ -1,11 +1,11 @@
 package net.kemitix.thorp.storage.aws
 
-import cats.data.EitherT
-import cats.effect.IO
 import com.amazonaws.services.s3.AmazonS3
 import net.kemitix.thorp.domain.StorageQueueEvent.ShutdownQueueEvent
 import net.kemitix.thorp.domain._
 import net.kemitix.thorp.storage.api.StorageService
+import zio.console.Console
+import zio.{Task, TaskR}
 
 class S3StorageService(
     amazonS3Client: => AmazonS3,
@@ -20,7 +20,7 @@ class S3StorageService(
   override def listObjects(
       bucket: Bucket,
       prefix: RemoteKey
-  )(implicit l: Logger): EitherT[IO, String, S3ObjectsData] =
+  ): TaskR[Console, S3ObjectsData] =
     objectLister.listObjects(bucket, prefix)
 
   override def copy(
@@ -28,7 +28,7 @@ class S3StorageService(
       sourceKey: RemoteKey,
       hash: MD5Hash,
       targetKey: RemoteKey
-  ): IO[StorageQueueEvent] =
+  ): Task[StorageQueueEvent] =
     copier.copy(bucket, sourceKey, hash, targetKey)
 
   override def upload(
@@ -37,17 +37,17 @@ class S3StorageService(
       batchMode: Boolean,
       uploadEventListener: UploadEventListener,
       tryCount: Int
-  ): IO[StorageQueueEvent] =
+  ): Task[StorageQueueEvent] =
     uploader.upload(localFile, bucket, batchMode, uploadEventListener, 1)
 
   override def delete(
       bucket: Bucket,
       remoteKey: RemoteKey
-  ): IO[StorageQueueEvent] =
+  ): Task[StorageQueueEvent] =
     deleter.delete(bucket, remoteKey)
 
-  override def shutdown: IO[StorageQueueEvent] =
-    IO {
+  override def shutdown: Task[StorageQueueEvent] =
+    Task {
       amazonTransferManager.shutdownNow(true)
       amazonS3Client.shutdown()
       ShutdownQueueEvent()
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Uploader.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Uploader.scala
index b4f46cb..3d6e84e 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Uploader.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/Uploader.scala
@@ -1,9 +1,7 @@
 package net.kemitix.thorp.storage.aws
 
-import cats.effect.IO
 import com.amazonaws.event.{ProgressEvent, ProgressEventType, ProgressListener}
 import com.amazonaws.services.s3.model.{ObjectMetadata, PutObjectRequest}
-import com.amazonaws.services.s3.transfer.model.UploadResult
 import net.kemitix.thorp.domain.StorageQueueEvent.{
   ErrorQueueEvent,
   UploadQueueEvent
@@ -14,8 +12,7 @@ import net.kemitix.thorp.domain.UploadEvent.{
   TransferEvent
 }
 import net.kemitix.thorp.domain.{StorageQueueEvent, _}
-
-import scala.util.Try
+import zio.Task
 
 class Uploader(transferManager: => AmazonTransferManager) {
 
@@ -25,29 +22,24 @@ class Uploader(transferManager: => AmazonTransferManager) {
       batchMode: Boolean,
       uploadEventListener: UploadEventListener,
       tryCount: Int
-  ): IO[StorageQueueEvent] =
+  ): Task[StorageQueueEvent] =
     for {
       upload <- transfer(localFile, bucket, batchMode, uploadEventListener)
-      action = upload match {
-        case Right(r) =>
-          UploadQueueEvent(RemoteKey(r.getKey), MD5Hash(r.getETag))
-        case Left(e) => ErrorQueueEvent(localFile.remoteKey, e)
-      }
-    } yield action
+    } yield upload
 
   private def transfer(
       localFile: LocalFile,
       bucket: Bucket,
       batchMode: Boolean,
       uploadEventListener: UploadEventListener
-  ): IO[Either[Throwable, UploadResult]] = {
+  ): Task[StorageQueueEvent] = {
     val listener: ProgressListener = progressListener(uploadEventListener)
     val putObjectRequest           = request(localFile, bucket, batchMode, listener)
-    IO {
-      Try(transferManager.upload(putObjectRequest))
-        .map(_.waitForUploadResult)
-        .toEither
-    }
+    Task(transferManager.upload(putObjectRequest))
+      .map(_.waitForUploadResult)
+      .map(upload =>
+        UploadQueueEvent(RemoteKey(upload.getKey), MD5Hash(upload.getETag)))
+      .catchAll(e => Task.succeed(ErrorQueueEvent(localFile.remoteKey, e)))
   }
 
   private def request(
diff --git a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/DummyLogger.scala b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/DummyLogger.scala
deleted file mode 100644
index 9600a3f..0000000
--- a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/DummyLogger.scala
+++ /dev/null
@@ -1,18 +0,0 @@
-package net.kemitix.thorp.storage.aws
-
-import cats.effect.IO
-import net.kemitix.thorp.domain.Logger
-
-class DummyLogger extends Logger {
-
-  override def debug(message: => String): IO[Unit] = IO.unit
-
-  override def info(message: => String): IO[Unit] = IO.unit
-
-  override def warn(message: String): IO[Unit] = IO.unit
-
-  override def error(message: String): IO[Unit] = IO.unit
-
-  override def withDebug(debug: Boolean): Logger = this
-
-}
diff --git a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/ETagGeneratorTest.scala b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/ETagGeneratorTest.scala
index 96625f0..eb901bc 100644
--- a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/ETagGeneratorTest.scala
+++ b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/ETagGeneratorTest.scala
@@ -1,18 +1,21 @@
 package net.kemitix.thorp.storage.aws
 
+import java.nio.file.Path
+
 import com.amazonaws.services.s3.transfer.TransferManagerConfiguration
 import net.kemitix.thorp.core.Resource
-import net.kemitix.thorp.domain.MD5Hash
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 class ETagGeneratorTest extends FunSpec {
 
+  private val runtime = new DefaultRuntime {}
+
   private val bigFile       = Resource(this, "big-file")
   private val bigFilePath   = bigFile.toPath
   private val configuration = new TransferManagerConfiguration
   private val chunkSize     = 1200000
   configuration.setMinimumUploadPartSize(chunkSize)
-  private val logger = new DummyLogger
 
   describe("Create offsets") {
     it("should create offsets") {
@@ -25,10 +28,6 @@ class ETagGeneratorTest extends FunSpec {
     }
   }
 
-  def test(expected: String, result: MD5Hash): Unit = {
-    assertResult(expected)(result.hash)
-  }
-
   describe("create md5 hash for each chunk") {
     it("should create expected hash for chunks") {
       val md5Hashes = List(
@@ -40,20 +39,26 @@ class ETagGeneratorTest extends FunSpec {
       ).zipWithIndex
       md5Hashes.foreach {
         case (hash, index) =>
-          test(hash,
-               ETagGenerator
-                 .hashChunk(bigFilePath, index, chunkSize)(logger)
-                 .unsafeRunSync)
+          assertResult(Right(hash))(
+            invoke(bigFilePath, index, chunkSize).map(_.hash))
       }
     }
+    def invoke(path: Path, index: Long, size: Long) =
+      runtime.unsafeRunSync {
+        ETagGenerator.hashChunk(path, index, size)
+      }.toEither
   }
 
   describe("create etag for whole file") {
     val expected = "f14327c90ad105244c446c498bfe9a7d-2"
     it("should match aws etag for the file") {
-      val result = ETagGenerator.eTag(bigFilePath)(logger).unsafeRunSync
-      assertResult(expected)(result)
+      val result = invoke(bigFilePath)
+      assertResult(Right(expected))(result)
     }
+    def invoke(path: Path) =
+      runtime.unsafeRunSync {
+        ETagGenerator.eTag(path)
+      }.toEither
   }
 
 }
diff --git a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/S3StorageServiceSuite.scala b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/S3StorageServiceSuite.scala
index 5caa112..f6ff943 100644
--- a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/S3StorageServiceSuite.scala
+++ b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/S3StorageServiceSuite.scala
@@ -14,16 +14,18 @@ import net.kemitix.thorp.core.Resource
 import net.kemitix.thorp.domain._
 import org.scalamock.scalatest.MockFactory
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 class S3StorageServiceSuite extends FunSpec with MockFactory {
 
+  private val runtime = new DefaultRuntime {}
+
   describe("listObjectsInPrefix") {
     val source     = Resource(this, "upload")
     val sourcePath = source.toPath
     val prefix     = RemoteKey("prefix")
     implicit val config: Config =
       Config(Bucket("bucket"), prefix, sources = Sources(List(sourcePath)))
-    implicit val implLogger: Logger = new DummyLogger
 
     val lm = LastModified(Instant.now.truncatedTo(ChronoUnit.MILLIS))
 
@@ -73,12 +75,15 @@ class S3StorageServiceSuite extends FunSpec with MockFactory {
                       k1b -> HashModified(h1, lm),
                       k2  -> HashModified(h2, lm))
         ))
-      val result = storageService
-        .listObjects(Bucket("bucket"), RemoteKey("prefix"))
-        .value
-        .unsafeRunSync
+      val result = invoke(storageService)
       assertResult(expected)(result)
     }
   }
 
+  private def invoke(storageService: S3StorageService) =
+    runtime.unsafeRunSync {
+      storageService
+        .listObjects(Bucket("bucket"), RemoteKey("prefix"))
+    }.toEither
+
 }
diff --git a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/StorageServiceSuite.scala b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/StorageServiceSuite.scala
index 0f77280..71764c7 100644
--- a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/StorageServiceSuite.scala
+++ b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/StorageServiceSuite.scala
@@ -20,7 +20,6 @@ class StorageServiceSuite extends FunSpec with MockFactory {
   private val prefix = RemoteKey("prefix")
   implicit private val config: Config =
     Config(Bucket("bucket"), prefix, sources = Sources(List(sourcePath)))
-  implicit private val implLogger: Logger = new DummyLogger
   private val fileToKey =
     KeyGenerator.generateKey(config.sources, config.prefix) _
 
diff --git a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/UploaderSuite.scala b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/UploaderSuite.scala
index ad2f4ad..0f6909c 100644
--- a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/UploaderSuite.scala
+++ b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/UploaderSuite.scala
@@ -17,8 +17,7 @@ class UploaderSuite extends FunSpec with MockFactory {
   private val prefix             = RemoteKey("prefix")
   implicit private val config: Config =
     Config(Bucket("bucket"), prefix, sources = Sources(List(sourcePath)))
-  private val fileToKey                   = generateKey(config.sources, config.prefix) _
-  implicit private val implLogger: Logger = new DummyLogger
+  private val fileToKey = generateKey(config.sources, config.prefix) _
 
   def md5HashMap(hash: MD5Hash): Map[String, MD5Hash] = Map("md5" -> hash)