diff --git a/build.sbt b/build.sbt
index f7eddbd..6f46ceb 100644
--- a/build.sbt
+++ b/build.sbt
@@ -135,3 +135,4 @@ lazy val domain = (project in file("domain"))
   .settings(commonSettings)
   .settings(assemblyJarName in assembly := "domain.jar")
   .settings(testDependencies)
+  .settings(zioDependencies)
diff --git a/config/src/main/scala/net/kemitix/thorp/config/ConfigValidation.scala b/config/src/main/scala/net/kemitix/thorp/config/ConfigValidation.scala
index 23ab79c..1d0d769 100644
--- a/config/src/main/scala/net/kemitix/thorp/config/ConfigValidation.scala
+++ b/config/src/main/scala/net/kemitix/thorp/config/ConfigValidation.scala
@@ -1,6 +1,6 @@
 package net.kemitix.thorp.config
 
-import java.nio.file.Path
+import java.io.File
 
 sealed trait ConfigValidation {
 
@@ -22,10 +22,10 @@ object ConfigValidation {
   }
 
   case class ErrorReadingFile(
-      path: Path,
+      file: File,
       message: String
   ) extends ConfigValidation {
-    override def errorMessage: String = s"Error reading file '$path': $message"
+    override def errorMessage: String = s"Error reading file '$file': $message"
   }
 
 }
diff --git a/config/src/main/scala/net/kemitix/thorp/config/ConfigurationBuilder.scala b/config/src/main/scala/net/kemitix/thorp/config/ConfigurationBuilder.scala
index 3b4fd07..b046269 100644
--- a/config/src/main/scala/net/kemitix/thorp/config/ConfigurationBuilder.scala
+++ b/config/src/main/scala/net/kemitix/thorp/config/ConfigurationBuilder.scala
@@ -1,6 +1,6 @@
 package net.kemitix.thorp.config
 
-import java.nio.file.Paths
+import java.io.File
 
 import net.kemitix.thorp.filesystem.FileSystem
 import zio.ZIO
@@ -11,9 +11,9 @@ import zio.ZIO
   */
 trait ConfigurationBuilder {
 
-  private val userConfigFilename = ".config/thorp.conf"
-  private val globalConfig       = Paths.get("/etc/thorp.conf")
-  private val userHome           = Paths.get(System.getProperty("user.home"))
+  private val userConfigFile = ".config/thorp.conf"
+  private val globalConfig   = new File("/etc/thorp.conf")
+  private val userHome       = new File(System.getProperty("user.home"))
 
   def buildConfig(priorityOpts: ConfigOptions)
     : ZIO[FileSystem, ConfigValidationException, Configuration] =
@@ -33,7 +33,7 @@ trait ConfigurationBuilder {
 
   private def userOptions(priorityOpts: ConfigOptions) =
     if (ConfigQuery.ignoreUserOptions(priorityOpts)) emptyConfig
-    else ParseConfigFile.parseFile(userHome.resolve(userConfigFilename))
+    else ParseConfigFile.parseFile(new File(userHome, userConfigFile))
 
   private def globalOptions(priorityOpts: ConfigOptions) =
     if (ConfigQuery.ignoreGlobalOptions(priorityOpts)) emptyConfig
diff --git a/config/src/main/scala/net/kemitix/thorp/config/ParseConfigFile.scala b/config/src/main/scala/net/kemitix/thorp/config/ParseConfigFile.scala
index 142ee52..2f68094 100644
--- a/config/src/main/scala/net/kemitix/thorp/config/ParseConfigFile.scala
+++ b/config/src/main/scala/net/kemitix/thorp/config/ParseConfigFile.scala
@@ -1,6 +1,6 @@
 package net.kemitix.thorp.config
 
-import java.nio.file.Path
+import java.io.File
 
 import net.kemitix.thorp.filesystem.FileSystem
 import zio.{IO, TaskR, ZIO}
@@ -8,19 +8,14 @@ import zio.{IO, TaskR, ZIO}
 trait ParseConfigFile {
 
   def parseFile(
-      filename: Path): ZIO[FileSystem, Seq[ConfigValidation], ConfigOptions] =
-    (readFile(filename) >>= ParseConfigLines.parseLines)
-      .catchAll(
-        h =>
-          IO.fail(
-            List(ConfigValidation.ErrorReadingFile(filename, h.getMessage))))
+      file: File): ZIO[FileSystem, Seq[ConfigValidation], ConfigOptions] =
+    (FileSystem.exists(file) >>= readLines(file) >>= ParseConfigLines.parseLines)
+      .catchAll(h =>
+        IO.fail(List(ConfigValidation.ErrorReadingFile(file, h.getMessage))))
 
-  private def readFile(filename: Path) =
-    FileSystem.exists(filename.toFile) >>= readLines(filename)
-
-  private def readLines(filename: Path)(
+  private def readLines(file: File)(
       exists: Boolean): TaskR[FileSystem, Seq[String]] =
-    if (exists) FileSystem.lines(filename.toFile)
+    if (exists) FileSystem.lines(file)
     else ZIO.succeed(Seq.empty)
 
 }
diff --git a/config/src/main/scala/net/kemitix/thorp/config/SourceConfigLoader.scala b/config/src/main/scala/net/kemitix/thorp/config/SourceConfigLoader.scala
index ae941b1..cc5daa8 100644
--- a/config/src/main/scala/net/kemitix/thorp/config/SourceConfigLoader.scala
+++ b/config/src/main/scala/net/kemitix/thorp/config/SourceConfigLoader.scala
@@ -1,5 +1,7 @@
 package net.kemitix.thorp.config
 
+import java.io.File
+
 import net.kemitix.thorp.domain.Sources
 import net.kemitix.thorp.filesystem.FileSystem
 import zio.ZIO
@@ -12,7 +14,7 @@ trait SourceConfigLoader {
       sources: Sources): ZIO[FileSystem, Seq[ConfigValidation], ConfigOptions] =
     ZIO
       .foreach(sources.paths) { path =>
-        ParseConfigFile.parseFile(path.resolve(thorpConfigFileName))
+        ParseConfigFile.parseFile(new File(path.toFile, thorpConfigFileName))
       }
       .map(_.foldLeft(ConfigOptions(sources.paths.map(ConfigOption.Source))) {
         (acc, co) =>
diff --git a/config/src/test/scala/net/kemitix/thorp/config/ParseConfigFileTest.scala b/config/src/test/scala/net/kemitix/thorp/config/ParseConfigFileTest.scala
index c3b62a6..6d38968 100644
--- a/config/src/test/scala/net/kemitix/thorp/config/ParseConfigFileTest.scala
+++ b/config/src/test/scala/net/kemitix/thorp/config/ParseConfigFileTest.scala
@@ -1,47 +1,58 @@
 package net.kemitix.thorp.config
 
-import java.nio.file.{Path, Paths}
+import java.io.File
+import java.nio.file.Paths
 
+import net.kemitix.thorp.domain.TemporaryFolder
 import net.kemitix.thorp.filesystem.FileSystem
 import org.scalatest.FunSpec
 import zio.DefaultRuntime
 
-class ParseConfigFileTest extends FunSpec {
+class ParseConfigFileTest extends FunSpec with TemporaryFolder {
 
   private val empty = Right(ConfigOptions())
 
   describe("parse a missing file") {
-    val filename = Paths.get("/path/to/missing/file")
+    val file = new File("/path/to/missing/file")
     it("should return no options") {
-      assertResult(empty)(invoke(filename))
+      assertResult(empty)(invoke(file))
     }
   }
   describe("parse an empty file") {
-    val filename = Resource(this, "empty-file").toPath
     it("should return no options") {
-      assertResult(empty)(invoke(filename))
+      withDirectory(dir => {
+        val file = writeFile(dir, "empty-file")
+        assertResult(empty)(invoke(file))
+      })
     }
   }
   describe("parse a file with no valid entries") {
-    val filename = Resource(this, "invalid-config").toPath
     it("should return no options") {
-      assertResult(empty)(invoke(filename))
+      withDirectory(dir => {
+        val file = writeFile(dir, "invalid-config", "no valid = config items")
+        assertResult(empty)(invoke(file))
+      })
     }
   }
   describe("parse a file with properties") {
-    val filename = Resource(this, "simple-config").toPath
-    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))
+      val expected = Right(
+        ConfigOptions(List(ConfigOption.Source(Paths.get("/path/to/source")),
+                           ConfigOption.Bucket("bucket-name"))))
+      withDirectory(dir => {
+        val file = writeFile(dir,
+                             "simple-config",
+                             "source = /path/to/source",
+                             "bucket = bucket-name")
+        assertResult(expected)(invoke(file))
+      })
     }
   }
 
-  private def invoke(filename: Path) = {
+  private def invoke(file: File) = {
     new DefaultRuntime {}.unsafeRunSync {
       ParseConfigFile
-        .parseFile(filename)
+        .parseFile(file)
         .provide(FileSystem.Live)
     }.toEither
   }
diff --git a/core/src/main/scala/net/kemitix/thorp/core/ActionGenerator.scala b/core/src/main/scala/net/kemitix/thorp/core/ActionGenerator.scala
index 05a0108..4bc68e4 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/ActionGenerator.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/ActionGenerator.scala
@@ -21,7 +21,7 @@ object ActionGenerator {
     s3MetaData match {
       // #1 local exists, remote exists, remote matches - do nothing
       case S3MetaData(localFile, _, Some(RemoteMetaData(key, hash, _)))
-          if localFile.matches(hash) =>
+          if LocalFile.matchesHash(localFile)(hash) =>
         doNothing(bucket, key)
       // #2 local exists, remote is missing, other matches - copy
       case S3MetaData(localFile, matchByHash, None) if matchByHash.nonEmpty =>
@@ -33,7 +33,7 @@ object ActionGenerator {
         uploadFile(bucket, localFile)
       // #4 local exists, remote exists, remote no match, other matches - copy
       case S3MetaData(localFile, matchByHash, Some(RemoteMetaData(_, hash, _)))
-          if !localFile.matches(hash) &&
+          if !LocalFile.matchesHash(localFile)(hash) &&
             matchByHash.nonEmpty =>
         copyFile(bucket, localFile, matchByHash)
       // #5 local exists, remote exists, remote no match, other no matches - upload
diff --git a/core/src/main/scala/net/kemitix/thorp/core/Filters.scala b/core/src/main/scala/net/kemitix/thorp/core/Filters.scala
new file mode 100644
index 0000000..6b21b0f
--- /dev/null
+++ b/core/src/main/scala/net/kemitix/thorp/core/Filters.scala
@@ -0,0 +1,41 @@
+package net.kemitix.thorp.core
+
+import java.nio.file.Path
+
+import net.kemitix.thorp.domain.Filter
+import net.kemitix.thorp.domain.Filter.{Exclude, Include}
+
+object Filters {
+
+  def isIncluded(p: Path)(filters: List[Filter]): Boolean = {
+    sealed trait State
+    case class Unknown()   extends State
+    case class Accepted()  extends State
+    case class Discarded() extends State
+    val excluded = isExcludedByFilter(p)(_)
+    val included = isIncludedByFilter(p)(_)
+    filters.foldRight(Unknown(): State)((filter, state) =>
+      (filter, state) match {
+        case (_, Accepted())                => Accepted()
+        case (_, Discarded())               => Discarded()
+        case (x: Exclude, _) if excluded(x) => Discarded()
+        case (i: Include, _) if included(i) => Accepted()
+        case _                              => Unknown()
+    }) match {
+      case Accepted()  => true
+      case Discarded() => false
+      case Unknown() =>
+        filters.forall {
+          case _: Include => false
+          case _          => true
+        }
+    }
+  }
+
+  def isIncludedByFilter(path: Path)(filter: Filter): Boolean =
+    filter.predicate.test(path.toString)
+
+  def isExcludedByFilter(path: Path)(filter: Filter): Boolean =
+    filter.predicate.test(path.toString)
+
+}
diff --git a/core/src/main/scala/net/kemitix/thorp/core/KeyGenerator.scala b/core/src/main/scala/net/kemitix/thorp/core/KeyGenerator.scala
index fb8711f..04bfaf5 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/KeyGenerator.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/KeyGenerator.scala
@@ -3,21 +3,17 @@ package net.kemitix.thorp.core
 import java.nio.file.Path
 
 import net.kemitix.thorp.domain.{RemoteKey, Sources}
+import zio.Task
 
 object KeyGenerator {
 
   def generateKey(
       sources: Sources,
       prefix: RemoteKey
-  )(path: Path): RemoteKey = {
-    val source       = sources.forPath(path)
-    val relativePath = source.relativize(path.toAbsolutePath).toString
-    RemoteKey(
-      List(
-        prefix.key,
-        relativePath
-      ).filter(_.nonEmpty)
-        .mkString("/"))
-  }
+  )(path: Path): Task[RemoteKey] =
+    Sources
+      .forPath(path)(sources)
+      .map(p => p.relativize(path.toAbsolutePath).toString)
+      .map(RemoteKey.resolve(_)(prefix))
 
 }
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 c1972bf..a7e4603 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/LocalFileStream.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/LocalFileStream.scala
@@ -4,9 +4,8 @@ import java.io.File
 import java.nio.file.Path
 
 import net.kemitix.thorp.config.Config
-import net.kemitix.thorp.core.KeyGenerator.generateKey
 import net.kemitix.thorp.core.hasher.Hasher
-import net.kemitix.thorp.domain._
+import net.kemitix.thorp.domain.Sources
 import net.kemitix.thorp.filesystem.FileSystem
 import zio.{Task, TaskR, ZIO}
 
@@ -48,21 +47,18 @@ object LocalFileStream {
         .filter({ case (_, included) => included })
         .map({ case (path, _) => path })
 
-  private def localFile(path: Path) = {
-    val file = path.toFile
+  private def localFile(path: Path) =
     for {
       sources <- Config.sources
       prefix  <- Config.prefix
+      source  <- Sources.forPath(path)(sources)
       hash    <- Hasher.hashObject(path)
-      localFile = LocalFile(file,
-                            sources.forPath(path).toFile,
-                            hash,
-                            generateKey(sources, prefix)(path))
-    } yield
-      LocalFiles(localFiles = Stream(localFile),
-                 count = 1,
-                 totalSizeBytes = file.length)
-  }
+      localFile <- LocalFileValidator.validate(path,
+                                               source.toFile,
+                                               hash,
+                                               sources,
+                                               prefix)
+    } yield LocalFiles.one(localFile)
 
   private def listFiles(path: Path) =
     for {
@@ -78,6 +74,6 @@ object LocalFileStream {
   private def isIncluded(path: Path) =
     for {
       filters <- Config.filters
-    } yield Filter.isIncluded(path)(filters)
+    } yield Filters.isIncluded(path)(filters)
 
 }
diff --git a/core/src/main/scala/net/kemitix/thorp/core/LocalFileValidator.scala b/core/src/main/scala/net/kemitix/thorp/core/LocalFileValidator.scala
new file mode 100644
index 0000000..b1f5592
--- /dev/null
+++ b/core/src/main/scala/net/kemitix/thorp/core/LocalFileValidator.scala
@@ -0,0 +1,66 @@
+package net.kemitix.thorp.core
+
+import java.io.File
+import java.nio.file.Path
+
+import net.kemitix.thorp.domain.{
+  HashType,
+  LocalFile,
+  MD5Hash,
+  RemoteKey,
+  Sources
+}
+import zio.{IO, ZIO}
+
+object LocalFileValidator {
+
+  def validate(
+      path: Path,
+      source: File,
+      hash: Map[HashType, MD5Hash],
+      sources: Sources,
+      prefix: RemoteKey
+  ): IO[Violation, LocalFile] =
+    for {
+      vFile     <- validateFile(path.toFile)
+      remoteKey <- validateRemoteKey(sources, prefix, path)
+    } yield LocalFile(vFile, source, hash, remoteKey)
+
+  private def validateFile(file: File) =
+    if (file.isDirectory)
+      ZIO.fail(Violation.IsNotAFile(file))
+    else
+      ZIO.succeed(file)
+
+  private def validateRemoteKey(sources: Sources,
+                                prefix: RemoteKey,
+                                path: Path) =
+    KeyGenerator
+      .generateKey(sources, prefix)(path)
+      .mapError(e => Violation.InvalidRemoteKey(path, e))
+
+  sealed trait Violation extends Throwable {
+    def getMessage: String
+  }
+  object Violation {
+    case class IsNotAFile(file: File) extends Violation {
+      override def getMessage: String = s"Local File must be a file: ${file}"
+    }
+    case class InvalidRemoteKey(path: Path, e: Throwable) extends Violation {
+      override def getMessage: String =
+        s"Remote Key for '${path}' is invalid: ${e.getMessage}"
+    }
+  }
+
+  def resolve(
+      path: String,
+      md5Hashes: Map[HashType, MD5Hash],
+      source: Path,
+      sources: Sources,
+      prefix: RemoteKey
+  ): IO[Violation, LocalFile] = {
+    val resolvedPath = source.resolve(path)
+    validate(resolvedPath, source.toFile, md5Hashes, sources, prefix)
+  }
+
+}
diff --git a/core/src/main/scala/net/kemitix/thorp/core/LocalFiles.scala b/core/src/main/scala/net/kemitix/thorp/core/LocalFiles.scala
index c70f0f7..2693abe 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/LocalFiles.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/LocalFiles.scala
@@ -13,12 +13,11 @@ case class LocalFiles(
       count = count + append.count,
       totalSizeBytes = totalSizeBytes + append.totalSizeBytes
     )
-
 }
 
 object LocalFiles {
-
   def reduce: Stream[LocalFiles] => LocalFiles =
     list => list.foldLeft(LocalFiles())((acc, lf) => acc ++ lf)
-
+  def one(localFile: LocalFile): LocalFiles =
+    LocalFiles(Stream(localFile), 1, localFile.file.length)
 }
diff --git a/core/src/main/scala/net/kemitix/thorp/core/Remote.scala b/core/src/main/scala/net/kemitix/thorp/core/Remote.scala
index e9902d6..d9a2b2a 100644
--- a/core/src/main/scala/net/kemitix/thorp/core/Remote.scala
+++ b/core/src/main/scala/net/kemitix/thorp/core/Remote.scala
@@ -18,7 +18,7 @@ object Remote {
       remoteKey: RemoteKey
   ): TaskR[FileSystem, Boolean] = {
     def existsInSource(source: Path) =
-      remoteKey.asFile(source, prefix) match {
+      RemoteKey.asFile(source, prefix)(remoteKey) match {
         case Some(file) => FileSystem.exists(file)
         case None       => ZIO.succeed(false)
       }
diff --git a/core/src/test/scala/net/kemitix/thorp/core/ActionGeneratorSuite.scala b/core/src/test/scala/net/kemitix/thorp/core/ActionGeneratorSuite.scala
index 4e97e2d..d7fc107 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/ActionGeneratorSuite.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/ActionGeneratorSuite.scala
@@ -2,13 +2,7 @@ package net.kemitix.thorp.core
 
 import java.time.Instant
 
-import net.kemitix.thorp.config.{
-  Config,
-  ConfigOption,
-  ConfigOptions,
-  ConfigurationBuilder,
-  Resource
-}
+import net.kemitix.thorp.config._
 import net.kemitix.thorp.core.Action.{DoNothing, ToCopy, ToUpload}
 import net.kemitix.thorp.domain.HashType.MD5
 import net.kemitix.thorp.domain._
@@ -31,8 +25,6 @@ class ActionGeneratorSuite extends FunSpec {
       ConfigOption.IgnoreUserOptions,
       ConfigOption.IgnoreGlobalOptions
     ))
-  private val fileToKey =
-    KeyGenerator.generateKey(sources, prefix) _
 
   describe("create actions") {
 
@@ -40,119 +32,156 @@ class ActionGeneratorSuite extends FunSpec {
 
     describe("#1 local exists, remote exists, remote matches - do nothing") {
       val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val theRemoteMetadata =
-        RemoteMetaData(theFile.remoteKey, theHash, lastModified)
-      val input =
-        S3MetaData(theFile, // local exists
-                   matchByHash = Set(theRemoteMetadata), // remote matches
-                   matchByKey = Some(theRemoteMetadata) // remote exists
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        theRemoteMetadata = RemoteMetaData(theFile.remoteKey,
+                                           theHash,
+                                           lastModified)
+        input = S3MetaData(
+          theFile, // local exists
+          matchByHash = Set(theRemoteMetadata), // remote matches
+          matchByKey = Some(theRemoteMetadata) // remote exists
         )
+      } yield (theFile, input)
       it("do nothing") {
-        val expected =
-          Right(
-            Stream(DoNothing(bucket, theFile.remoteKey, theFile.file.length)))
-        val result = invoke(input, previousActions)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, input) => {
+            val expected =
+              Right(Stream(
+                DoNothing(bucket, theFile.remoteKey, theFile.file.length + 1)))
+            val result = invoke(input, previousActions)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
     describe("#2 local exists, remote is missing, other matches - copy") {
       val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val theRemoteKey   = theFile.remoteKey
-      val otherRemoteKey = prefix.resolve("other-key")
-      val otherRemoteMetadata =
-        RemoteMetaData(otherRemoteKey, theHash, lastModified)
-      val input =
-        S3MetaData(theFile, // local exists
-                   matchByHash = Set(otherRemoteMetadata), // other matches
-                   matchByKey = None) // remote is missing
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        theRemoteKey   = theFile.remoteKey
+        otherRemoteKey = RemoteKey.resolve("other-key")(prefix)
+        otherRemoteMetadata = RemoteMetaData(otherRemoteKey,
+                                             theHash,
+                                             lastModified)
+        input = S3MetaData(
+          theFile, // local exists
+          matchByHash = Set(otherRemoteMetadata), // other matches
+          matchByKey = None) // remote is missing
+      } yield (theFile, theRemoteKey, input, otherRemoteKey)
       it("copy from other key") {
-        val expected = Right(
-          Stream(
-            ToCopy(bucket,
-                   otherRemoteKey,
-                   theHash,
-                   theRemoteKey,
-                   theFile.file.length))) // copy
-        val result = invoke(input, previousActions)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, theRemoteKey, input, otherRemoteKey) => {
+            val expected = Right(
+              Stream(
+                ToCopy(bucket,
+                       otherRemoteKey,
+                       theHash,
+                       theRemoteKey,
+                       theFile.file.length))) // copy
+            val result = invoke(input, previousActions)
+            assertResult(expected)(result)
+          }
+        })
       }
-    }
-    describe("#3 local exists, remote is missing, other no matches - upload") {
-      val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val input = S3MetaData(theFile, // local exists
+      describe("#3 local exists, remote is missing, other no matches - upload") {
+        val theHash = MD5Hash("the-hash")
+        val env = for {
+          theFile <- LocalFileValidator.resolve("the-file",
+                                                md5HashMap(theHash),
+                                                sourcePath,
+                                                sources,
+                                                prefix)
+          input = S3MetaData(theFile, // local exists
                              matchByHash = Set.empty, // other no matches
                              matchByKey = None) // remote is missing
-      it("upload") {
-        val expected = Right(
-          Stream(ToUpload(bucket, theFile, theFile.file.length))) // upload
-        val result = invoke(input, previousActions)
-        assertResult(expected)(result)
+        } yield (theFile, input)
+        it("upload") {
+          env.map({
+            case (theFile, input) => {
+              val expected = Right(Stream(
+                ToUpload(bucket, theFile, theFile.file.length))) // upload
+              val result = invoke(input, previousActions)
+              assertResult(expected)(result)
+            }
+          })
+        }
       }
     }
     describe(
       "#4 local exists, remote exists, remote no match, other matches - copy") {
       val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val theRemoteKey   = theFile.remoteKey
-      val oldHash        = MD5Hash("old-hash")
-      val otherRemoteKey = prefix.resolve("other-key")
-      val otherRemoteMetadata =
-        RemoteMetaData(otherRemoteKey, theHash, lastModified)
-      val oldRemoteMetadata = RemoteMetaData(theRemoteKey,
-                                             hash = oldHash, // remote no match
-                                             lastModified = lastModified)
-      val input =
-        S3MetaData(theFile, // local exists
-                   matchByHash = Set(otherRemoteMetadata), // other matches
-                   matchByKey = Some(oldRemoteMetadata)) // remote exists
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        theRemoteKey   = theFile.remoteKey
+        oldHash        = MD5Hash("old-hash")
+        otherRemoteKey = RemoteKey.resolve("other-key")(prefix)
+        otherRemoteMetadata = RemoteMetaData(otherRemoteKey,
+                                             theHash,
+                                             lastModified)
+        oldRemoteMetadata = RemoteMetaData(theRemoteKey,
+                                           hash = oldHash, // remote no match
+                                           lastModified = lastModified)
+        input = S3MetaData(
+          theFile, // local exists
+          matchByHash = Set(otherRemoteMetadata), // other matches
+          matchByKey = Some(oldRemoteMetadata)) // remote exists
+      } yield (theFile, theRemoteKey, input, otherRemoteKey)
       it("copy from other key") {
-        val expected = Right(
-          Stream(
-            ToCopy(bucket,
-                   otherRemoteKey,
-                   theHash,
-                   theRemoteKey,
-                   theFile.file.length))) // copy
-        val result = invoke(input, previousActions)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, theRemoteKey, input, otherRemoteKey) => {
+            val expected = Right(
+              Stream(
+                ToCopy(bucket,
+                       otherRemoteKey,
+                       theHash,
+                       theRemoteKey,
+                       theFile.file.length))) // copy
+            val result = invoke(input, previousActions)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
     describe(
       "#5 local exists, remote exists, remote no match, other no matches - upload") {
       val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val theRemoteKey = theFile.remoteKey
-      val oldHash      = MD5Hash("old-hash")
-      val theRemoteMetadata =
-        RemoteMetaData(theRemoteKey, oldHash, lastModified)
-      val input =
-        S3MetaData(theFile, // local exists
-                   matchByHash = Set.empty, // remote no match, other no match
-                   matchByKey = Some(theRemoteMetadata) // remote exists
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        theRemoteKey      = theFile.remoteKey
+        oldHash           = MD5Hash("old-hash")
+        theRemoteMetadata = RemoteMetaData(theRemoteKey, oldHash, lastModified)
+        input = S3MetaData(
+          theFile, // local exists
+          matchByHash = Set.empty, // remote no match, other no match
+          matchByKey = Some(theRemoteMetadata) // remote exists
         )
+      } yield (theFile, input)
       it("upload") {
-        val expected = Right(
-          Stream(ToUpload(bucket, theFile, theFile.file.length))) // upload
-        val result = invoke(input, previousActions)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, input) => {
+            val expected = Right(
+              Stream(ToUpload(bucket, theFile, theFile.file.length))) // upload
+            val result = invoke(input, previousActions)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
     describe("#6 local missing, remote exists - delete") {
diff --git a/domain/src/test/scala/net/kemitix/thorp/domain/FiltersSuite.scala b/core/src/test/scala/net/kemitix/thorp/core/FiltersSuite.scala
similarity index 79%
rename from domain/src/test/scala/net/kemitix/thorp/domain/FiltersSuite.scala
rename to core/src/test/scala/net/kemitix/thorp/core/FiltersSuite.scala
index 3523c2f..00279da 100644
--- a/domain/src/test/scala/net/kemitix/thorp/domain/FiltersSuite.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/FiltersSuite.scala
@@ -1,7 +1,8 @@
-package net.kemitix.thorp.domain
+package net.kemitix.thorp.core
 
 import java.nio.file.Paths
 
+import net.kemitix.thorp.domain.Filter
 import net.kemitix.thorp.domain.Filter.{Exclude, Include}
 import org.scalatest.FunSpec
 
@@ -21,31 +22,32 @@ class FiltersSuite extends FunSpec {
     describe("default filter") {
       val include = Include()
       it("should include files") {
-        paths.foreach(path => assertResult(true)(include.isIncluded(path)))
+        paths.foreach(path =>
+          assertResult(true)(Filters.isIncludedByFilter(path)(include)))
       }
     }
     describe("directory exact match include '/upload/subdir/'") {
       val include = Include("/upload/subdir/")
       it("include matching directory") {
         val matching = Paths.get("/upload/subdir/leaf-file")
-        assertResult(true)(include.isIncluded(matching))
+        assertResult(true)(Filters.isIncludedByFilter(matching)(include))
       }
       it("exclude non-matching files") {
         val nonMatching = Paths.get("/upload/other-file")
-        assertResult(false)(include.isIncluded(nonMatching))
+        assertResult(false)(Filters.isIncludedByFilter(nonMatching)(include))
       }
     }
     describe("file partial match 'root'") {
       val include = Include("root")
       it("include matching file '/upload/root-file") {
         val matching = Paths.get("/upload/root-file")
-        assertResult(true)(include.isIncluded(matching))
+        assertResult(true)(Filters.isIncludedByFilter(matching)(include))
       }
       it("exclude non-matching files 'test-file-for-hash.txt' & '/upload/subdir/leaf-file'") {
         val nonMatching1 = Paths.get("/test-file-for-hash.txt")
         val nonMatching2 = Paths.get("/upload/subdir/leaf-file")
-        assertResult(false)(include.isIncluded(nonMatching1))
-        assertResult(false)(include.isIncluded(nonMatching2))
+        assertResult(false)(Filters.isIncludedByFilter(nonMatching1)(include))
+        assertResult(false)(Filters.isIncludedByFilter(nonMatching2)(include))
       }
     }
   }
@@ -63,30 +65,30 @@ class FiltersSuite extends FunSpec {
       val exclude = Exclude("/upload/subdir/")
       it("exclude matching directory") {
         val matching = Paths.get("/upload/subdir/leaf-file")
-        assertResult(true)(exclude.isExcluded(matching))
+        assertResult(true)(Filters.isExcludedByFilter(matching)(exclude))
       }
       it("include non-matching files") {
         val nonMatching = Paths.get("/upload/other-file")
-        assertResult(false)(exclude.isExcluded(nonMatching))
+        assertResult(false)(Filters.isExcludedByFilter(nonMatching)(exclude))
       }
     }
     describe("file partial match 'root'") {
       val exclude = Exclude("root")
       it("exclude matching file '/upload/root-file") {
         val matching = Paths.get("/upload/root-file")
-        assertResult(true)(exclude.isExcluded(matching))
+        assertResult(true)(Filters.isExcludedByFilter(matching)(exclude))
       }
       it("include non-matching files 'test-file-for-hash.txt' & '/upload/subdir/leaf-file'") {
         val nonMatching1 = Paths.get("/test-file-for-hash.txt")
         val nonMatching2 = Paths.get("/upload/subdir/leaf-file")
-        assertResult(false)(exclude.isExcluded(nonMatching1))
-        assertResult(false)(exclude.isExcluded(nonMatching2))
+        assertResult(false)(Filters.isExcludedByFilter(nonMatching1)(exclude))
+        assertResult(false)(Filters.isExcludedByFilter(nonMatching2)(exclude))
       }
     }
   }
   describe("isIncluded") {
     def invoke(filters: List[Filter]) = {
-      paths.filter(path => Filter.isIncluded(path)(filters))
+      paths.filter(path => Filters.isIncluded(path)(filters))
     }
 
     describe("when there are no filters") {
diff --git a/core/src/test/scala/net/kemitix/thorp/core/KeyGeneratorSuite.scala b/core/src/test/scala/net/kemitix/thorp/core/KeyGeneratorSuite.scala
index f541c20..61f3cfa 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/KeyGeneratorSuite.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/KeyGeneratorSuite.scala
@@ -1,10 +1,12 @@
 package net.kemitix.thorp.core
 
 import java.io.File
+import java.nio.file.Path
 
 import net.kemitix.thorp.config.Resource
 import net.kemitix.thorp.domain.{RemoteKey, Sources}
 import org.scalatest.FunSpec
+import zio.DefaultRuntime
 
 class KeyGeneratorSuite extends FunSpec {
 
@@ -12,26 +14,32 @@ class KeyGeneratorSuite extends FunSpec {
   private val sourcePath   = source.toPath
   private val prefix       = RemoteKey("prefix")
   private val sources      = Sources(List(sourcePath))
-  private val fileToKey =
-    KeyGenerator.generateKey(sources, prefix) _
 
   describe("key generator") {
 
     describe("when file is within source") {
       it("has a valid key") {
-        val subdir = "subdir"
-        assertResult(RemoteKey(s"${prefix.key}/$subdir"))(
-          fileToKey(sourcePath.resolve(subdir)))
+        val subdir   = "subdir"
+        val expected = Right(RemoteKey(s"${prefix.key}/$subdir"))
+        val result   = invoke(sourcePath.resolve(subdir))
+        assertResult(expected)(result)
       }
     }
 
     describe("when file is deeper within source") {
       it("has a valid key") {
-        val subdir = "subdir/deeper/still"
-        assertResult(RemoteKey(s"${prefix.key}/$subdir"))(
-          fileToKey(sourcePath.resolve(subdir)))
+        val subdir   = "subdir/deeper/still"
+        val expected = Right(RemoteKey(s"${prefix.key}/$subdir"))
+        val result   = invoke(sourcePath.resolve(subdir))
+        assertResult(expected)(result)
       }
     }
+
+    def invoke(path: Path) = {
+      new DefaultRuntime {}.unsafeRunSync {
+        KeyGenerator.generateKey(sources, prefix)(path)
+      }.toEither
+    }
   }
 
 }
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 17b5755..642206d 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/LocalFileStreamSuite.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/LocalFileStreamSuite.scala
@@ -32,7 +32,7 @@ class LocalFileStreamSuite extends FunSpec {
       val result =
         invoke()
           .map(_.localFiles)
-          .map(_.map(_.relative.toString))
+          .map(_.map(LocalFile.relativeToSource(_).toString))
           .map(_.toSet)
       assertResult(expected)(result)
     }
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 c5fe30c..7919635 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/PlanBuilderTest.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/PlanBuilderTest.scala
@@ -333,13 +333,17 @@ class PlanBuilderTest extends FreeSpec with TemporaryFolder {
                        md5Hash: MD5Hash,
                        source: Path,
                        file: File): (String, String, String, String, String) =
-    ("upload", remoteKey.key, md5Hash.hash, source.toString, file.toString)
+    ("upload",
+     remoteKey.key,
+     MD5Hash.hash(md5Hash),
+     source.toString,
+     file.toString)
 
   private def toCopy(
       sourceKey: RemoteKey,
       md5Hash: MD5Hash,
       targetKey: RemoteKey): (String, String, String, String, String) =
-    ("copy", sourceKey.key, md5Hash.hash, targetKey.key, "")
+    ("copy", sourceKey.key, MD5Hash.hash(md5Hash), targetKey.key, "")
 
   private def toDelete(
       remoteKey: RemoteKey): (String, String, String, String, String) =
@@ -386,12 +390,12 @@ class PlanBuilderTest extends FreeSpec with TemporaryFolder {
       case ToUpload(_, lf, _) =>
         ("upload",
          lf.remoteKey.key,
-         lf.hashes(MD5).hash,
+         MD5Hash.hash(lf.hashes(MD5)),
          lf.source.toString,
          lf.file.toString)
       case ToDelete(_, remoteKey, _) => ("delete", remoteKey.key, "", "", "")
       case ToCopy(_, sourceKey, hash, targetKey, _) =>
-        ("copy", sourceKey.key, hash.hash, targetKey.key, "")
+        ("copy", sourceKey.key, MD5Hash.hash(hash), targetKey.key, "")
       case DoNothing(_, remoteKey, _) =>
         ("do-nothing", remoteKey.key, "", "", "")
       case x => ("other", x.toString, "", "", "")
diff --git a/core/src/test/scala/net/kemitix/thorp/core/S3MetaDataEnricherSuite.scala b/core/src/test/scala/net/kemitix/thorp/core/S3MetaDataEnricherSuite.scala
index 05eb4a5..b6afcb4 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/S3MetaDataEnricherSuite.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/S3MetaDataEnricherSuite.scala
@@ -14,8 +14,6 @@ class S3MetaDataEnricherSuite extends FunSpec {
   private val sourcePath = source.toPath
   private val sources    = Sources(List(sourcePath))
   private val prefix     = RemoteKey("prefix")
-  private val fileToKey =
-    KeyGenerator.generateKey(sources, prefix) _
 
   def getMatchesByKey(
       status: (Option[HashModified], Set[(MD5Hash, KeyModified)]))
@@ -36,138 +34,180 @@ class S3MetaDataEnricherSuite extends FunSpec {
     describe(
       "#1a local exists, remote exists, remote matches, other matches - do nothing") {
       val theHash: MD5Hash = MD5Hash("the-file-hash")
-      val theFile: LocalFile = LocalFile.resolve("the-file",
-                                                 md5HashMap(theHash),
-                                                 sourcePath,
-                                                 fileToKey)
-      val theRemoteKey: RemoteKey = theFile.remoteKey
-      val s3: S3ObjectsData = S3ObjectsData(
-        byHash = Map(theHash     -> Set(KeyModified(theRemoteKey, lastModified))),
-        byKey = Map(theRemoteKey -> HashModified(theHash, lastModified))
-      )
-      val theRemoteMetadata =
-        RemoteMetaData(theRemoteKey, theHash, lastModified)
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        theRemoteKey = theFile.remoteKey
+        s3 = S3ObjectsData(
+          byHash = Map(theHash     -> Set(KeyModified(theRemoteKey, lastModified))),
+          byKey = Map(theRemoteKey -> HashModified(theHash, lastModified))
+        )
+        theRemoteMetadata = RemoteMetaData(theRemoteKey, theHash, lastModified)
+      } yield (theFile, theRemoteMetadata, s3)
       it("generates valid metadata") {
-        val expected = S3MetaData(theFile,
-                                  matchByHash = Set(theRemoteMetadata),
-                                  matchByKey = Some(theRemoteMetadata))
-        val result = getMetadata(theFile, s3)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, theRemoteMetadata, s3) => {
+            val expected = S3MetaData(theFile,
+                                      matchByHash = Set(theRemoteMetadata),
+                                      matchByKey = Some(theRemoteMetadata))
+            val result = getMetadata(theFile, s3)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
     describe(
       "#1b local exists, remote exists, remote matches, other no matches - do nothing") {
       val theHash: MD5Hash = MD5Hash("the-file-hash")
-      val theFile: LocalFile = LocalFile.resolve("the-file",
-                                                 md5HashMap(theHash),
-                                                 sourcePath,
-                                                 fileToKey)
-      val theRemoteKey: RemoteKey = prefix.resolve("the-file")
-      val s3: S3ObjectsData = S3ObjectsData(
-        byHash = Map(theHash     -> Set(KeyModified(theRemoteKey, lastModified))),
-        byKey = Map(theRemoteKey -> HashModified(theHash, lastModified))
-      )
-      val theRemoteMetadata =
-        RemoteMetaData(theRemoteKey, theHash, lastModified)
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        theRemoteKey: RemoteKey = RemoteKey.resolve("the-file")(prefix)
+        s3: S3ObjectsData = S3ObjectsData(
+          byHash = Map(theHash     -> Set(KeyModified(theRemoteKey, lastModified))),
+          byKey = Map(theRemoteKey -> HashModified(theHash, lastModified))
+        )
+        theRemoteMetadata = RemoteMetaData(theRemoteKey, theHash, lastModified)
+      } yield (theFile, theRemoteMetadata, s3)
       it("generates valid metadata") {
-        val expected = S3MetaData(theFile,
-                                  matchByHash = Set(theRemoteMetadata),
-                                  matchByKey = Some(theRemoteMetadata))
-        val result = getMetadata(theFile, s3)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, theRemoteMetadata, s3) => {
+            val expected = S3MetaData(theFile,
+                                      matchByHash = Set(theRemoteMetadata),
+                                      matchByKey = Some(theRemoteMetadata))
+            val result = getMetadata(theFile, s3)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
     describe(
       "#2 local exists, remote is missing, remote no match, other matches - copy") {
       val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val otherRemoteKey = RemoteKey("other-key")
-      val s3: S3ObjectsData = S3ObjectsData(
-        byHash = Map(theHash       -> Set(KeyModified(otherRemoteKey, lastModified))),
-        byKey = Map(otherRemoteKey -> HashModified(theHash, lastModified))
-      )
-      val otherRemoteMetadata =
-        RemoteMetaData(otherRemoteKey, theHash, lastModified)
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        otherRemoteKey = RemoteKey("other-key")
+        s3: S3ObjectsData = S3ObjectsData(
+          byHash =
+            Map(theHash              -> Set(KeyModified(otherRemoteKey, lastModified))),
+          byKey = Map(otherRemoteKey -> HashModified(theHash, lastModified))
+        )
+        otherRemoteMetadata = RemoteMetaData(otherRemoteKey,
+                                             theHash,
+                                             lastModified)
+      } yield (theFile, otherRemoteMetadata, s3)
       it("generates valid metadata") {
-        val expected = S3MetaData(theFile,
-                                  matchByHash = Set(otherRemoteMetadata),
-                                  matchByKey = None)
-        val result = getMetadata(theFile, s3)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, otherRemoteMetadata, s3) => {
+            val expected = S3MetaData(theFile,
+                                      matchByHash = Set(otherRemoteMetadata),
+                                      matchByKey = None)
+            val result = getMetadata(theFile, s3)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
     describe(
       "#3 local exists, remote is missing, remote no match, other no matches - upload") {
       val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val s3: S3ObjectsData = S3ObjectsData()
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        s3: S3ObjectsData = S3ObjectsData()
+      } yield (theFile, s3)
       it("generates valid metadata") {
-        val expected =
-          S3MetaData(theFile, matchByHash = Set.empty, matchByKey = None)
-        val result = getMetadata(theFile, s3)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, s3) => {
+            val expected =
+              S3MetaData(theFile, matchByHash = Set.empty, matchByKey = None)
+            val result = getMetadata(theFile, s3)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
     describe(
       "#4 local exists, remote exists, remote no match, other matches - copy") {
       val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val theRemoteKey   = theFile.remoteKey
-      val oldHash        = MD5Hash("old-hash")
-      val otherRemoteKey = prefix.resolve("other-key")
-      val s3: S3ObjectsData = S3ObjectsData(
-        byHash = Map(oldHash -> Set(KeyModified(theRemoteKey, lastModified)),
-                     theHash -> Set(KeyModified(otherRemoteKey, lastModified))),
-        byKey = Map(
-          theRemoteKey   -> HashModified(oldHash, lastModified),
-          otherRemoteKey -> HashModified(theHash, lastModified)
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        theRemoteKey   = theFile.remoteKey
+        oldHash        = MD5Hash("old-hash")
+        otherRemoteKey = RemoteKey.resolve("other-key")(prefix)
+        s3: S3ObjectsData = S3ObjectsData(
+          byHash =
+            Map(oldHash -> Set(KeyModified(theRemoteKey, lastModified)),
+                theHash -> Set(KeyModified(otherRemoteKey, lastModified))),
+          byKey = Map(
+            theRemoteKey   -> HashModified(oldHash, lastModified),
+            otherRemoteKey -> HashModified(theHash, lastModified)
+          )
         )
-      )
-      val theRemoteMetadata =
-        RemoteMetaData(theRemoteKey, oldHash, lastModified)
-      val otherRemoteMetadata =
-        RemoteMetaData(otherRemoteKey, theHash, lastModified)
+        theRemoteMetadata = RemoteMetaData(theRemoteKey, oldHash, lastModified)
+        otherRemoteMetadata = RemoteMetaData(otherRemoteKey,
+                                             theHash,
+                                             lastModified)
+      } yield (theFile, theRemoteMetadata, otherRemoteMetadata, s3)
       it("generates valid metadata") {
-        val expected = S3MetaData(theFile,
-                                  matchByHash = Set(otherRemoteMetadata),
-                                  matchByKey = Some(theRemoteMetadata))
-        val result = getMetadata(theFile, s3)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, theRemoteMetadata, otherRemoteMetadata, s3) => {
+            val expected = S3MetaData(theFile,
+                                      matchByHash = Set(otherRemoteMetadata),
+                                      matchByKey = Some(theRemoteMetadata))
+            val result = getMetadata(theFile, s3)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
     describe(
       "#5 local exists, remote exists, remote no match, other no matches - upload") {
       val theHash = MD5Hash("the-hash")
-      val theFile = LocalFile.resolve("the-file",
-                                      md5HashMap(theHash),
-                                      sourcePath,
-                                      fileToKey)
-      val theRemoteKey = theFile.remoteKey
-      val oldHash      = MD5Hash("old-hash")
-      val s3: S3ObjectsData = S3ObjectsData(
-        byHash = Map(oldHash -> Set(KeyModified(theRemoteKey, lastModified)),
-                     theHash -> Set.empty),
-        byKey = Map(
-          theRemoteKey -> HashModified(oldHash, lastModified)
+      val env = for {
+        theFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(theHash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+        theRemoteKey = theFile.remoteKey
+        oldHash      = MD5Hash("old-hash")
+        s3: S3ObjectsData = S3ObjectsData(
+          byHash = Map(oldHash -> Set(KeyModified(theRemoteKey, lastModified)),
+                       theHash -> Set.empty),
+          byKey = Map(
+            theRemoteKey -> HashModified(oldHash, lastModified)
+          )
         )
-      )
-      val theRemoteMetadata =
-        RemoteMetaData(theRemoteKey, oldHash, lastModified)
+        theRemoteMetadata = RemoteMetaData(theRemoteKey, oldHash, lastModified)
+      } yield (theFile, theRemoteMetadata, s3)
       it("generates valid metadata") {
-        val expected = S3MetaData(theFile,
-                                  matchByHash = Set.empty,
-                                  matchByKey = Some(theRemoteMetadata))
-        val result = getMetadata(theFile, s3)
-        assertResult(expected)(result)
+        env.map({
+          case (theFile, theRemoteMetadata, s3) => {
+            val expected = S3MetaData(theFile,
+                                      matchByHash = Set.empty,
+                                      matchByKey = Some(theRemoteMetadata))
+            val result = getMetadata(theFile, s3)
+            assertResult(expected)(result)
+          }
+        })
       }
     }
   }
@@ -178,71 +218,103 @@ class S3MetaDataEnricherSuite extends FunSpec {
 
   describe("getS3Status") {
     val hash = MD5Hash("hash")
-    val localFile =
-      LocalFile.resolve("the-file", md5HashMap(hash), sourcePath, fileToKey)
-    val key = localFile.remoteKey
-    val keyOtherKey = LocalFile.resolve("other-key-same-hash",
-                                        md5HashMap(hash),
-                                        sourcePath,
-                                        fileToKey)
-    val diffHash = MD5Hash("diff")
-    val keyDiffHash = LocalFile.resolve("other-key-diff-hash",
-                                        md5HashMap(diffHash),
-                                        sourcePath,
-                                        fileToKey)
-    val lastModified = LastModified(Instant.now)
-    val s3ObjectsData: S3ObjectsData = S3ObjectsData(
-      byHash = Map(
-        hash -> Set(KeyModified(key, lastModified),
-                    KeyModified(keyOtherKey.remoteKey, lastModified)),
-        diffHash -> Set(KeyModified(keyDiffHash.remoteKey, lastModified))
-      ),
-      byKey = Map(
-        key                   -> HashModified(hash, lastModified),
-        keyOtherKey.remoteKey -> HashModified(hash, lastModified),
-        keyDiffHash.remoteKey -> HashModified(diffHash, lastModified)
+    val env = for {
+      localFile <- LocalFileValidator.resolve("the-file",
+                                              md5HashMap(hash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+      key = localFile.remoteKey
+      keyOtherKey <- LocalFileValidator.resolve("other-key-same-hash",
+                                                md5HashMap(hash),
+                                                sourcePath,
+                                                sources,
+                                                prefix)
+      diffHash = MD5Hash("diff")
+      keyDiffHash <- LocalFileValidator.resolve("other-key-diff-hash",
+                                                md5HashMap(diffHash),
+                                                sourcePath,
+                                                sources,
+                                                prefix)
+      lastModified = LastModified(Instant.now)
+      s3ObjectsData = S3ObjectsData(
+        byHash = Map(
+          hash -> Set(KeyModified(key, lastModified),
+                      KeyModified(keyOtherKey.remoteKey, lastModified)),
+          diffHash -> Set(KeyModified(keyDiffHash.remoteKey, lastModified))
+        ),
+        byKey = Map(
+          key                   -> HashModified(hash, lastModified),
+          keyOtherKey.remoteKey -> HashModified(hash, lastModified),
+          keyDiffHash.remoteKey -> HashModified(diffHash, lastModified)
+        )
       )
-    )
+    } yield (s3ObjectsData, localFile, keyDiffHash, diffHash)
 
-    def invoke(localFile: LocalFile) = {
+    def invoke(localFile: LocalFile, s3ObjectsData: S3ObjectsData) = {
       getS3Status(localFile, s3ObjectsData)
     }
 
     describe("when remote key exists") {
       it("should return a result for matching key") {
-        val result = getMatchesByKey(invoke(localFile))
-        assert(result.contains(HashModified(hash, lastModified)))
+        env.map({
+          case (s3ObjectsData, localFile: LocalFile, _, _) =>
+            val result = getMatchesByKey(invoke(localFile, s3ObjectsData))
+            assert(result.contains(HashModified(hash, lastModified)))
+        })
       }
     }
 
     describe("when remote key does not exist and no others matches hash") {
-      val localFile = LocalFile.resolve("missing-file",
-                                        md5HashMap(MD5Hash("unique")),
-                                        sourcePath,
-                                        fileToKey)
+      val env2 = for {
+        localFile <- LocalFileValidator.resolve("missing-remote",
+                                                md5HashMap(MD5Hash("unique")),
+                                                sourcePath,
+                                                sources,
+                                                prefix)
+      } yield (localFile)
       it("should return no matches by key") {
-        val result = getMatchesByKey(invoke(localFile))
-        assert(result.isEmpty)
+        env.map({
+          case (s3ObjectsData, _, _, _) => {
+            env2.map({
+              case (localFile) => {
+                val result = getMatchesByKey(invoke(localFile, s3ObjectsData))
+                assert(result.isEmpty)
+              }
+            })
+          }
+        })
       }
       it("should return no matches by hash") {
-        val result = getMatchesByHash(invoke(localFile))
-        assert(result.isEmpty)
+        env.map({
+          case (s3ObjectsData, _, _, _) => {
+            env2.map({
+              case (localFile) => {
+                val result = getMatchesByHash(invoke(localFile, s3ObjectsData))
+                assert(result.isEmpty)
+              }
+            })
+          }
+        })
       }
     }
 
     describe("when remote key exists and no others match hash") {
-      it("should return match by key") {
-        val result = getMatchesByKey(invoke(keyDiffHash))
-        assert(result.contains(HashModified(diffHash, lastModified)))
-      }
-      it("should return only itself in match by hash") {
-        val result = getMatchesByHash(invoke(keyDiffHash))
-        assert(
-          result.equals(
-            Set((diffHash, KeyModified(keyDiffHash.remoteKey, lastModified)))))
-      }
+      env.map({
+        case (s3ObjectsData, _, keyDiffHash, diffHash) => {
+          it("should return match by key") {
+            val result = getMatchesByKey(invoke(keyDiffHash, s3ObjectsData))
+            assert(result.contains(HashModified(diffHash, lastModified)))
+          }
+          it("should return only itself in match by hash") {
+            val result = getMatchesByHash(invoke(keyDiffHash, s3ObjectsData))
+            assert(
+              result.equals(Set(
+                (diffHash, KeyModified(keyDiffHash.remoteKey, lastModified)))))
+          }
+        }
+      })
     }
-
   }
 
 }
diff --git a/core/src/test/scala/net/kemitix/thorp/core/hasher/MD5HashGeneratorTest.scala b/core/src/test/scala/net/kemitix/thorp/core/hasher/MD5HashGeneratorTest.scala
index 7237e4f..7ccc624 100644
--- a/core/src/test/scala/net/kemitix/thorp/core/hasher/MD5HashGeneratorTest.scala
+++ b/core/src/test/scala/net/kemitix/thorp/core/hasher/MD5HashGeneratorTest.scala
@@ -3,6 +3,7 @@ package net.kemitix.thorp.core.hasher
 import java.nio.file.Path
 
 import net.kemitix.thorp.config.Resource
+import net.kemitix.thorp.domain.MD5Hash
 import net.kemitix.thorp.domain.MD5HashData.{BigFile, Root}
 import net.kemitix.thorp.filesystem.FileSystem
 import org.scalatest.FunSpec
@@ -42,14 +43,14 @@ class MD5HashGeneratorTest extends FunSpec {
       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)
+        val expected = Right(MD5Hash.hash(part1.hash))
+        val result   = invoke(path, part1.offset, part1.size).map(MD5Hash.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)
+        val expected = Right(MD5Hash.hash(part2.hash))
+        val result   = invoke(path, part2.offset, part2.size).map(MD5Hash.hash)
         assertResult(expected)(result)
       }
     }
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/Filter.scala b/domain/src/main/scala/net/kemitix/thorp/domain/Filter.scala
index 3a730b8..208d70e 100644
--- a/domain/src/main/scala/net/kemitix/thorp/domain/Filter.scala
+++ b/domain/src/main/scala/net/kemitix/thorp/domain/Filter.scala
@@ -1,53 +1,18 @@
 package net.kemitix.thorp.domain
 
-import java.nio.file.Path
+import java.util.function.Predicate
 import java.util.regex.Pattern
 
-sealed trait Filter
+sealed trait Filter {
+  def predicate: Predicate[String]
+}
 
 object Filter {
-
-  def isIncluded(p: Path)(filters: List[Filter]): Boolean = {
-    sealed trait State
-    case class Unknown()   extends State
-    case class Accepted()  extends State
-    case class Discarded() extends State
-    filters.foldRight(Unknown(): State)((filter, state) =>
-      (filter, state) match {
-        case (_, Accepted())                    => Accepted()
-        case (_, Discarded())                   => Discarded()
-        case (x: Exclude, _) if x.isExcluded(p) => Discarded()
-        case (i: Include, _) if i.isIncluded(p) => Accepted()
-        case _                                  => Unknown()
-    }) match {
-      case Accepted()  => true
-      case Discarded() => false
-      case Unknown() =>
-        filters.forall {
-          case _: Include => false
-          case _          => true
-        }
-    }
+  case class Include(include: String = ".*") extends Filter {
+    lazy val predicate: Predicate[String] = Pattern.compile(include).asPredicate
   }
-
-  case class Include(
-      include: String = ".*"
-  ) extends Filter {
-
-    private lazy val predicate = Pattern.compile(include).asPredicate
-
-    def isIncluded(path: Path): Boolean = predicate.test(path.toString)
-
+  case class Exclude(exclude: String) extends Filter {
+    lazy val predicate: Predicate[String] =
+      Pattern.compile(exclude).asPredicate()
   }
-
-  case class Exclude(
-      exclude: String
-  ) extends Filter {
-
-    private lazy val predicate = Pattern.compile(exclude).asPredicate()
-
-    def isExcluded(path: Path): Boolean = predicate.test(path.toString)
-
-  }
-
 }
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/LocalFile.scala b/domain/src/main/scala/net/kemitix/thorp/domain/LocalFile.scala
index 10d8be2..bd47bc3 100644
--- a/domain/src/main/scala/net/kemitix/thorp/domain/LocalFile.scala
+++ b/domain/src/main/scala/net/kemitix/thorp/domain/LocalFile.scala
@@ -5,42 +5,22 @@ import java.nio.file.Path
 
 import net.kemitix.thorp.domain.HashType.MD5
 
-final case class LocalFile(
+final case class LocalFile private (
     file: File,
     source: File,
     hashes: Map[HashType, MD5Hash],
     remoteKey: RemoteKey
-) {
-
-  require(!file.isDirectory, s"LocalFile must not be a directory: $file")
-
-  def isDirectory: Boolean = file.isDirectory
-
-  // the path of the file within the source
-  def relative: Path = source.toPath.relativize(file.toPath)
-
-  def matches(other: MD5Hash): Boolean = hashes.values.exists(other equals _)
-
-  def md5base64: Option[String] = hashes.get(MD5).map(_.hash64)
-
-}
+)
 
 object LocalFile {
-
-  def resolve(
-      path: String,
-      md5Hashes: Map[HashType, MD5Hash],
-      source: Path,
-      pathToKey: Path => RemoteKey
-  ): LocalFile = {
-    val resolvedPath = source.resolve(path)
-    LocalFile(resolvedPath.toFile,
-              source.toFile,
-              md5Hashes,
-              pathToKey(resolvedPath))
-  }
-
   val remoteKey: SimpleLens[LocalFile, RemoteKey] =
     SimpleLens[LocalFile, RemoteKey](_.remoteKey,
                                      b => a => b.copy(remoteKey = a))
+  // the path of the file within the source
+  def relativeToSource(localFile: LocalFile): Path =
+    localFile.source.toPath.relativize(localFile.file.toPath)
+  def matchesHash(localFile: LocalFile)(other: MD5Hash): Boolean =
+    localFile.hashes.values.exists(other equals _)
+  def md5base64(localFile: LocalFile): Option[String] =
+    localFile.hashes.get(MD5).map(MD5Hash.hash64)
 }
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/Logger.scala b/domain/src/main/scala/net/kemitix/thorp/domain/Logger.scala
deleted file mode 100644
index 8862d74..0000000
--- a/domain/src/main/scala/net/kemitix/thorp/domain/Logger.scala
+++ /dev/null
@@ -1,15 +0,0 @@
-package net.kemitix.thorp.domain
-
-trait Logger {
-
-  // returns an instance of Logger with debug set as indicated
-  // where the current Logger already matches this state, then
-  // it returns itself, unmodified
-  def withDebug(debug: Boolean): Logger
-
-  def debug(message: => String): Unit
-  def info(message: => String): Unit
-  def warn(message: String): Unit
-  def error(message: String): Unit
-
-}
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/MD5Hash.scala b/domain/src/main/scala/net/kemitix/thorp/domain/MD5Hash.scala
index 4210f13..9d21a48 100644
--- a/domain/src/main/scala/net/kemitix/thorp/domain/MD5Hash.scala
+++ b/domain/src/main/scala/net/kemitix/thorp/domain/MD5Hash.scala
@@ -4,20 +4,14 @@ import java.util.Base64
 
 import net.kemitix.thorp.domain.QuoteStripper.stripQuotes
 
-final case class MD5Hash(
-    in: String
-) {
-
-  lazy val hash: String = in filter stripQuotes
-
-  lazy val digest: Array[Byte] = HexEncoder.decode(hash)
-
-  lazy val hash64: String = Base64.getEncoder.encodeToString(digest)
-}
+final case class MD5Hash(in: String)
 
 object MD5Hash {
-  def fromDigest(digest: Array[Byte]): MD5Hash = {
-    val hexDigest = (digest map ("%02x" format _)).mkString
-    MD5Hash(hexDigest)
-  }
+  def fromDigest(digest: Array[Byte]): MD5Hash =
+    MD5Hash((digest map ("%02x" format _)).mkString)
+  def hash(md5Hash: MD5Hash): String = md5Hash.in.filter(stripQuotes)
+  def digest(md5Hash: MD5Hash): Array[Byte] =
+    HexEncoder.decode(MD5Hash.hash(md5Hash))
+  def hash64(md5Hash: MD5Hash): String =
+    Base64.getEncoder.encodeToString(MD5Hash.digest(md5Hash))
 }
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/RemoteKey.scala b/domain/src/main/scala/net/kemitix/thorp/domain/RemoteKey.scala
index 65bcff0..e0d8362 100644
--- a/domain/src/main/scala/net/kemitix/thorp/domain/RemoteKey.scala
+++ b/domain/src/main/scala/net/kemitix/thorp/domain/RemoteKey.scala
@@ -3,31 +3,21 @@ package net.kemitix.thorp.domain
 import java.io.File
 import java.nio.file.{Path, Paths}
 
-final case class RemoteKey(
-    key: String
-) {
-
-  def asFile(
-      source: Path,
-      prefix: RemoteKey
-  ): Option[File] =
-    if (key.length == 0) None
-    else Some(source.resolve(relativeTo(prefix)).toFile)
-
-  private def relativeTo(prefix: RemoteKey) = {
-    prefix match {
-      case RemoteKey("") => Paths.get(key)
-      case _             => Paths.get(prefix.key).relativize(Paths.get(key))
-    }
-  }
-
-  def resolve(path: String): RemoteKey =
-    RemoteKey(List(key, path).filterNot(_.isEmpty).mkString("/"))
-
-}
+final case class RemoteKey(key: String)
 
 object RemoteKey {
   val key: SimpleLens[RemoteKey, String] =
     SimpleLens[RemoteKey, String](_.key, b => a => b.copy(key = a))
-
+  def asFile(source: Path, prefix: RemoteKey)(
+      remoteKey: RemoteKey): Option[File] =
+    if (remoteKey.key.length == 0) None
+    else Some(source.resolve(RemoteKey.relativeTo(prefix)(remoteKey)).toFile)
+  def relativeTo(prefix: RemoteKey)(remoteKey: RemoteKey): Path = {
+    prefix match {
+      case RemoteKey("") => Paths.get(remoteKey.key)
+      case _             => Paths.get(prefix.key).relativize(Paths.get(remoteKey.key))
+    }
+  }
+  def resolve(path: String)(remoteKey: RemoteKey): RemoteKey =
+    RemoteKey(List(remoteKey.key, path).filterNot(_.isEmpty).mkString("/"))
 }
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/Sources.scala b/domain/src/main/scala/net/kemitix/thorp/domain/Sources.scala
index 3bb13ef..0df7aba 100644
--- a/domain/src/main/scala/net/kemitix/thorp/domain/Sources.scala
+++ b/domain/src/main/scala/net/kemitix/thorp/domain/Sources.scala
@@ -2,6 +2,8 @@ package net.kemitix.thorp.domain
 
 import java.nio.file.Path
 
+import zio.{Task, ZIO}
+
 /**
   * The paths to synchronise with target.
   *
@@ -18,18 +20,10 @@ case class Sources(
   def +(path: Path)(implicit m: Monoid[Sources]): Sources = this ++ List(path)
   def ++(otherPaths: List[Path])(implicit m: Monoid[Sources]): Sources =
     m.op(this, Sources(otherPaths))
-
-  /**
-    * Returns the source path for the given path.
-    */
-  def forPath(path: Path): Path =
-    paths.find(source => path.startsWith(source)).get
 }
 
 object Sources {
-
   final val emptySources = Sources(List.empty)
-
   implicit def sourcesAppendMonoid: Monoid[Sources] = new Monoid[Sources] {
     override def zero: Sources = emptySources
     override def op(t1: Sources, t2: Sources): Sources =
@@ -38,4 +32,12 @@ object Sources {
         else acc ++ List(path)
       })
   }
+
+  /**
+    * Returns the source path for the given path.
+    */
+  def forPath(path: Path)(sources: Sources): Task[Path] =
+    ZIO
+      .fromOption(sources.paths.find(s => path.startsWith(s)))
+      .mapError(_ => new Exception("Path is not within any known source"))
 }
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/UploadEventListener.scala b/domain/src/main/scala/net/kemitix/thorp/domain/UploadEventListener.scala
index cb6b958..cff644f 100644
--- a/domain/src/main/scala/net/kemitix/thorp/domain/UploadEventListener.scala
+++ b/domain/src/main/scala/net/kemitix/thorp/domain/UploadEventListener.scala
@@ -1,10 +1,7 @@
 package net.kemitix.thorp.domain
 
 import net.kemitix.thorp.domain.UploadEvent.RequestEvent
-import net.kemitix.thorp.domain.UploadEventLogger.{
-  RequestCycle,
-  logRequestCycle
-}
+import net.kemitix.thorp.domain.UploadEventLogger.RequestCycle
 
 object UploadEventListener {
 
@@ -21,7 +18,7 @@ object UploadEventListener {
       uploadEvent match {
         case e: RequestEvent =>
           bytesTransferred += e.transferred
-          logRequestCycle(
+          UploadEventLogger(
             RequestCycle(settings.localFile,
                          bytesTransferred,
                          settings.index,
diff --git a/domain/src/main/scala/net/kemitix/thorp/domain/UploadEventLogger.scala b/domain/src/main/scala/net/kemitix/thorp/domain/UploadEventLogger.scala
index 6305212..00521e0 100644
--- a/domain/src/main/scala/net/kemitix/thorp/domain/UploadEventLogger.scala
+++ b/domain/src/main/scala/net/kemitix/thorp/domain/UploadEventLogger.scala
@@ -14,7 +14,7 @@ object UploadEventLogger {
       totalBytesSoFar: Long
   )
 
-  def logRequestCycle(requestCycle: RequestCycle): Unit = {
+  def apply(requestCycle: RequestCycle): Unit = {
     val remoteKey    = requestCycle.localFile.remoteKey.key
     val fileLength   = requestCycle.localFile.file.length
     val statusHeight = 7
diff --git a/domain/src/test/scala/net/kemitix/thorp/domain/MD5HashTest.scala b/domain/src/test/scala/net/kemitix/thorp/domain/MD5HashTest.scala
index 25c1510..12b5d7a 100644
--- a/domain/src/test/scala/net/kemitix/thorp/domain/MD5HashTest.scala
+++ b/domain/src/test/scala/net/kemitix/thorp/domain/MD5HashTest.scala
@@ -7,11 +7,11 @@ class MD5HashTest extends FunSpec {
   describe("recover base64 hash") {
     it("should recover base 64 #1") {
       val rootHash = MD5HashData.Root.hash
-      assertResult(MD5HashData.Root.base64)(rootHash.hash64)
+      assertResult(MD5HashData.Root.base64)(MD5Hash.hash64(rootHash))
     }
     it("should recover base 64 #2") {
       val leafHash = MD5HashData.Leaf.hash
-      assertResult(MD5HashData.Leaf.base64)(leafHash.hash64)
+      assertResult(MD5HashData.Leaf.base64)(MD5Hash.hash64(leafHash))
     }
   }
 }
diff --git a/domain/src/test/scala/net/kemitix/thorp/domain/RemoteKeyTest.scala b/domain/src/test/scala/net/kemitix/thorp/domain/RemoteKeyTest.scala
index b937fce..6bbc0f3 100644
--- a/domain/src/test/scala/net/kemitix/thorp/domain/RemoteKeyTest.scala
+++ b/domain/src/test/scala/net/kemitix/thorp/domain/RemoteKeyTest.scala
@@ -15,21 +15,21 @@ class RemoteKeyTest extends FreeSpec {
         val key      = emptyKey
         val path     = "path"
         val expected = RemoteKey("path")
-        val result   = key.resolve(path)
+        val result   = RemoteKey.resolve(path)(key)
         assertResult(expected)(result)
       }
       "when path is empty" in {
         val key      = RemoteKey("key")
         val path     = ""
         val expected = RemoteKey("key")
-        val result   = key.resolve(path)
+        val result   = RemoteKey.resolve(path)(key)
         assertResult(expected)(result)
       }
       "when key and path are empty" in {
         val key      = emptyKey
         val path     = ""
         val expected = emptyKey
-        val result   = key.resolve(path)
+        val result   = RemoteKey.resolve(path)(key)
         assertResult(expected)(result)
       }
     }
@@ -39,7 +39,7 @@ class RemoteKeyTest extends FreeSpec {
         val source   = Paths.get("source")
         val prefix   = RemoteKey("prefix")
         val expected = Some(new File("source/key"))
-        val result   = key.asFile(source, prefix)
+        val result   = RemoteKey.asFile(source, prefix)(key)
         assertResult(expected)(result)
       }
       "when prefix is empty" in {
@@ -47,7 +47,7 @@ class RemoteKeyTest extends FreeSpec {
         val source   = Paths.get("source")
         val prefix   = emptyKey
         val expected = Some(new File("source/key"))
-        val result   = key.asFile(source, prefix)
+        val result   = RemoteKey.asFile(source, prefix)(key)
         assertResult(expected)(result)
       }
       "when key is empty" in {
@@ -55,7 +55,7 @@ class RemoteKeyTest extends FreeSpec {
         val source   = Paths.get("source")
         val prefix   = RemoteKey("prefix")
         val expected = None
-        val result   = key.asFile(source, prefix)
+        val result   = RemoteKey.asFile(source, prefix)(key)
         assertResult(expected)(result)
       }
       "when key and prefix are empty" in {
@@ -63,7 +63,7 @@ class RemoteKeyTest extends FreeSpec {
         val source   = Paths.get("source")
         val prefix   = emptyKey
         val expected = None
-        val result   = key.asFile(source, prefix)
+        val result   = RemoteKey.asFile(source, prefix)(key)
         assertResult(expected)(result)
       }
     }
diff --git a/domain/src/test/scala/net/kemitix/thorp/domain/TemporaryFolder.scala b/domain/src/test/scala/net/kemitix/thorp/domain/TemporaryFolder.scala
index 4b481df..512b7aa 100644
--- a/domain/src/test/scala/net/kemitix/thorp/domain/TemporaryFolder.scala
+++ b/domain/src/test/scala/net/kemitix/thorp/domain/TemporaryFolder.scala
@@ -38,11 +38,13 @@ trait TemporaryFolder {
     path.resolve(name).toFile
   }
 
-  def writeFile(directory: Path, name: String, contents: String*): Unit = {
+  def writeFile(directory: Path, name: String, contents: String*): File = {
     directory.toFile.mkdirs
-    val pw = new PrintWriter(directory.resolve(name).toFile, "UTF-8")
-    contents.foreach(pw.println)
-    pw.close()
+    val file   = directory.resolve(name).toFile
+    val writer = new PrintWriter(file, "UTF-8")
+    contents.foreach(writer.println)
+    writer.close()
+    file
   }
 
 }
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 ca0e315..17436f4 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
@@ -41,7 +41,7 @@ trait Copier {
       copyRequest.sourceKey.key,
       copyRequest.bucket.name,
       copyRequest.targetKey.key
-    ).withMatchingETagConstraint(copyRequest.hash.hash)
+    ).withMatchingETagConstraint(MD5Hash.hash(copyRequest.hash))
 
   private def foldFailure(
       sourceKey: RemoteKey,
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 38cae23..08a618b 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
@@ -68,7 +68,7 @@ trait Uploader {
 
   private def metadata: LocalFile => ObjectMetadata = localFile => {
     val metadata = new ObjectMetadata()
-    localFile.md5base64.foreach(metadata.setContentMD5)
+    LocalFile.md5base64(localFile).foreach(metadata.setContentMD5)
     metadata
   }
 
diff --git a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/hasher/ETagGenerator.scala b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/hasher/ETagGenerator.scala
index ada93e4..b3f9265 100644
--- a/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/hasher/ETagGenerator.scala
+++ b/storage-aws/src/main/scala/net/kemitix/thorp/storage/aws/hasher/ETagGenerator.scala
@@ -7,6 +7,7 @@ import com.amazonaws.services.s3.transfer.TransferManagerConfiguration
 import com.amazonaws.services.s3.transfer.internal.TransferManagerUtils
 import net.kemitix.thorp.core.hasher.Hasher
 import net.kemitix.thorp.domain.HashType.MD5
+import net.kemitix.thorp.domain.MD5Hash
 import net.kemitix.thorp.filesystem.FileSystem
 import zio.{TaskR, ZIO}
 
@@ -56,7 +57,7 @@ private trait ETagGenerator {
     Hasher
       .hashObjectChunk(path, chunkNumber, chunkSize)
       .map(_(MD5))
-      .map(_.digest)
+      .map(MD5Hash.digest)
 
   def offsets(
       totalFileSizeBytes: Long,
diff --git a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/S3ObjectsByHashSuite.scala b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/S3ObjectsByHashSuite.scala
index 4c1805a..0babc7b 100644
--- a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/S3ObjectsByHashSuite.scala
+++ b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/S3ObjectsByHashSuite.scala
@@ -32,7 +32,7 @@ class S3ObjectsByHashSuite extends FunSpec {
                        remoteKey: RemoteKey,
                        lastModified: LastModified): S3ObjectSummary = {
     val summary = new S3ObjectSummary()
-    summary.setETag(md5Hash.hash)
+    summary.setETag(MD5Hash.hash(md5Hash))
     summary.setKey(remoteKey.key)
     summary.setLastModified(Date.from(lastModified.when))
     summary
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 5cec8f3..be21ccd 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
@@ -3,7 +3,7 @@ package net.kemitix.thorp.storage.aws
 import java.time.Instant
 
 import net.kemitix.thorp.config.Resource
-import net.kemitix.thorp.core.{KeyGenerator, S3MetaDataEnricher}
+import net.kemitix.thorp.core.{LocalFileValidator, S3MetaDataEnricher}
 import net.kemitix.thorp.domain.HashType.MD5
 import net.kemitix.thorp.domain._
 import org.scalamock.scalatest.MockFactory
@@ -15,39 +15,51 @@ class StorageServiceSuite extends FunSpec with MockFactory {
   private val sourcePath = source.toPath
   private val sources    = Sources(List(sourcePath))
   private val prefix     = RemoteKey("prefix")
-  private val fileToKey =
-    KeyGenerator.generateKey(sources, prefix) _
 
   describe("getS3Status") {
 
     val hash = MD5Hash("hash")
-    val localFile =
-      LocalFile.resolve("the-file", Map(MD5 -> hash), sourcePath, fileToKey)
-    val key = localFile.remoteKey
-    val keyOtherKey = LocalFile.resolve("other-key-same-hash",
-                                        Map(MD5 -> hash),
-                                        sourcePath,
-                                        fileToKey)
-    val diffHash = MD5Hash("diff")
-    val keyDiffHash = LocalFile.resolve("other-key-diff-hash",
-                                        Map(MD5 -> diffHash),
-                                        sourcePath,
-                                        fileToKey)
-    val lastModified = LastModified(Instant.now)
-    val s3ObjectsData: S3ObjectsData = S3ObjectsData(
-      byHash = Map(
-        hash -> Set(KeyModified(key, lastModified),
-                    KeyModified(keyOtherKey.remoteKey, lastModified)),
-        diffHash -> Set(KeyModified(keyDiffHash.remoteKey, lastModified))
-      ),
-      byKey = Map(
-        key                   -> HashModified(hash, lastModified),
-        keyOtherKey.remoteKey -> HashModified(hash, lastModified),
-        keyDiffHash.remoteKey -> HashModified(diffHash, lastModified)
+    val env = for {
+      localFile <- LocalFileValidator.resolve("the-file",
+                                              Map(MD5 -> hash),
+                                              sourcePath,
+                                              sources,
+                                              prefix)
+      key = localFile.remoteKey
+      keyOtherKey <- LocalFileValidator.resolve("other-key-same-hash",
+                                                Map(MD5 -> hash),
+                                                sourcePath,
+                                                sources,
+                                                prefix)
+      diffHash = MD5Hash("diff")
+      keyDiffHash <- LocalFileValidator.resolve("other-key-diff-hash",
+                                                Map(MD5 -> diffHash),
+                                                sourcePath,
+                                                sources,
+                                                prefix)
+      lastModified = LastModified(Instant.now)
+      s3ObjectsData = S3ObjectsData(
+        byHash = Map(
+          hash -> Set(KeyModified(key, lastModified),
+                      KeyModified(keyOtherKey.remoteKey, lastModified)),
+          diffHash -> Set(KeyModified(keyDiffHash.remoteKey, lastModified))
+        ),
+        byKey = Map(
+          key                   -> HashModified(hash, lastModified),
+          keyOtherKey.remoteKey -> HashModified(hash, lastModified),
+          keyDiffHash.remoteKey -> HashModified(diffHash, lastModified)
+        )
       )
-    )
+    } yield
+      (s3ObjectsData,
+       localFile: LocalFile,
+       lastModified,
+       keyOtherKey,
+       keyDiffHash,
+       diffHash,
+       key)
 
-    def invoke(localFile: LocalFile) =
+    def invoke(localFile: LocalFile, s3ObjectsData: S3ObjectsData) =
       S3MetaDataEnricher.getS3Status(localFile, s3ObjectsData)
 
     def getMatchesByKey(
@@ -67,47 +79,94 @@ class StorageServiceSuite extends FunSpec with MockFactory {
     describe(
       "when remote key exists, unmodified and other key matches the hash") {
       it("should return the match by key") {
-        val result = getMatchesByKey(invoke(localFile))
-        assert(result.contains(HashModified(hash, lastModified)))
+        env.map({
+          case (s3ObjectsData, localFile, lastModified, _, _, _, _) => {
+            val result = getMatchesByKey(invoke(localFile, s3ObjectsData))
+            assert(result.contains(HashModified(hash, lastModified)))
+          }
+        })
       }
       it("should return both matches for the hash") {
-        val result = getMatchesByHash(invoke(localFile))
-        assertResult(
-          Set((hash, KeyModified(key, lastModified)),
-              (hash, KeyModified(keyOtherKey.remoteKey, lastModified)))
-        )(result)
+        env.map({
+          case (s3ObjectsData,
+                localFile,
+                lastModified,
+                keyOtherKey,
+                _,
+                _,
+                key) => {
+            val result = getMatchesByHash(invoke(localFile, s3ObjectsData))
+            assertResult(
+              Set((hash, KeyModified(key, lastModified)),
+                  (hash, KeyModified(keyOtherKey.remoteKey, lastModified)))
+            )(result)
+          }
+        })
       }
     }
 
     describe("when remote key does not exist and no others matches hash") {
-      val localFile = LocalFile.resolve("missing-file",
-                                        Map(MD5 -> MD5Hash("unique")),
-                                        sourcePath,
-                                        fileToKey)
+      val env2 = LocalFileValidator
+        .resolve("missing-file",
+                 Map(MD5 -> MD5Hash("unique")),
+                 sourcePath,
+                 sources,
+                 prefix)
       it("should return no matches by key") {
-        val result = getMatchesByKey(invoke(localFile))
-        assert(result.isEmpty)
+        env2.map(localFile => {
+          env.map({
+            case (s3ObjectsData, _, _, _, _, _, _) => {
+              val result = getMatchesByKey(invoke(localFile, s3ObjectsData))
+              assert(result.isEmpty)
+            }
+          })
+        })
       }
       it("should return no matches by hash") {
-        val result = getMatchesByHash(invoke(localFile))
-        assert(result.isEmpty)
+        env2.map(localFile => {
+          env.map({
+            case (s3ObjectsData, _, _, _, _, _, _) => {
+              val result = getMatchesByHash(invoke(localFile, s3ObjectsData))
+              assert(result.isEmpty)
+            }
+          })
+        })
       }
     }
 
     describe("when remote key exists and no others match hash") {
-      val localFile = keyDiffHash
       it("should return the match by key") {
-        val result = getMatchesByKey(invoke(localFile))
-        assert(result.contains(HashModified(diffHash, lastModified)))
+        env.map({
+            case (s3ObjectsData,
+                  _,
+                  lastModified,
+                  _,
+                  keyDiffHash,
+                  diffHash,
+                  _) => {
+              val result = getMatchesByKey(invoke(keyDiffHash, s3ObjectsData))
+              assert(result.contains(HashModified(diffHash, lastModified)))
+            }
+          })
       }
       it("should return one match by hash") {
-        val result = getMatchesByHash(invoke(localFile))
-        assertResult(
-          Set((diffHash, KeyModified(keyDiffHash.remoteKey, lastModified)))
-        )(result)
+        env.map({
+            case (s3ObjectsData,
+                  _,
+                  lastModified,
+                  _,
+                  keyDiffHash,
+                  diffHash,
+                  _) => {
+              val result = getMatchesByHash(invoke(keyDiffHash, s3ObjectsData))
+              assertResult(
+                Set(
+                  (diffHash, KeyModified(keyDiffHash.remoteKey, lastModified)))
+              )(result)
+            }
+          })
       }
     }
-
   }
 
 }
diff --git a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/UploaderTest.scala b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/UploaderTest.scala
index a4891e2..0518e79 100644
--- a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/UploaderTest.scala
+++ b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/UploaderTest.scala
@@ -29,7 +29,7 @@ class UploaderTest extends FreeSpec with MockFactory {
     val bucket        = Bucket("aBucket")
     val uploadResult  = new UploadResult
     uploadResult.setKey(remoteKey.key)
-    uploadResult.setETag(aHash.hash)
+    uploadResult.setETag(MD5Hash.hash(aHash))
     val inProgress = new AmazonUpload.InProgress {
       override def waitForUploadResult: UploadResult = uploadResult
     }
diff --git a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/hasher/ETagGeneratorTest.scala b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/hasher/ETagGeneratorTest.scala
index 931943a..feb90a5 100644
--- a/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/hasher/ETagGeneratorTest.scala
+++ b/storage-aws/src/test/scala/net/kemitix/thorp/storage/aws/hasher/ETagGeneratorTest.scala
@@ -6,6 +6,7 @@ import com.amazonaws.services.s3.transfer.TransferManagerConfiguration
 import net.kemitix.thorp.config.Resource
 import net.kemitix.thorp.core.hasher.Hasher
 import net.kemitix.thorp.domain.HashType.MD5
+import net.kemitix.thorp.domain.MD5Hash
 import net.kemitix.thorp.filesystem.FileSystem
 import org.scalatest.FunSpec
 import zio.DefaultRuntime
@@ -45,7 +46,7 @@ class ETagGeneratorTest extends FunSpec {
           assertResult(Right(hash))(
             invoke(bigFilePath, index, chunkSize)
               .map(_(MD5))
-              .map(_.hash))
+              .map(MD5Hash.hash))
       }
     }
     def invoke(path: Path, index: Long, size: Long) =