diff --git a/src/main/scala/net/kemitix/s3thorp/Action.scala b/src/main/scala/net/kemitix/s3thorp/Action.scala
index f261ec5..6e6bc75 100644
--- a/src/main/scala/net/kemitix/s3thorp/Action.scala
+++ b/src/main/scala/net/kemitix/s3thorp/Action.scala
@@ -1,9 +1,10 @@
 package net.kemitix.s3thorp
 
 sealed trait Action
-case class DoNothing(remoteKey: RemoteKey) extends Action
-case class ToUpload(localFile: LocalFile) extends Action
-case class ToCopy(sourceKey: RemoteKey,
-                  hash: MD5Hash,
-                  targetKey: RemoteKey) extends Action
-case class ToDelete(remoteKey: RemoteKey) extends Action
+final case class DoNothing(remoteKey: RemoteKey) extends Action
+final case class ToUpload(localFile: LocalFile) extends Action
+final case class ToCopy(
+  sourceKey: RemoteKey,
+  hash: MD5Hash,
+  targetKey: RemoteKey) extends Action
+final case class ToDelete(remoteKey: RemoteKey) extends Action
diff --git a/src/main/scala/net/kemitix/s3thorp/Config.scala b/src/main/scala/net/kemitix/s3thorp/Config.scala
index b86a096..84c3a3b 100644
--- a/src/main/scala/net/kemitix/s3thorp/Config.scala
+++ b/src/main/scala/net/kemitix/s3thorp/Config.scala
@@ -2,15 +2,16 @@ package net.kemitix.s3thorp
 
 import java.io.File
 
-case class Config(bucket: Bucket = Bucket(""),
-                  prefix: RemoteKey = RemoteKey(""),
-                  verbose: Int = 1,
-                  filters: Seq[Filter] = List(),
-                  excludes: Seq[Exclude] = List(),
-                  multiPartThreshold: Long = 1024 * 1024 * 5,
-                  maxRetries: Int = 3,
-                  source: File
-               ) {
+final case class Config(
+  bucket: Bucket = Bucket(""),
+  prefix: RemoteKey = RemoteKey(""),
+  verbose: Int = 1,
+  filters: Seq[Filter] = List(),
+  excludes: Seq[Exclude] = List(),
+  multiPartThreshold: Long = 1024 * 1024 * 5,
+  maxRetries: Int = 3,
+  source: File
+) {
   require(source.isDirectory, s"Source must be a directory: $source")
   require(multiPartThreshold >= 1024 * 1024 * 5, s"Threshold for multi-part upload is 5Mb: '$multiPartThreshold'")
 }
diff --git a/src/main/scala/net/kemitix/s3thorp/Counters.scala b/src/main/scala/net/kemitix/s3thorp/Counters.scala
new file mode 100644
index 0000000..ee9dd1b
--- /dev/null
+++ b/src/main/scala/net/kemitix/s3thorp/Counters.scala
@@ -0,0 +1,6 @@
+package net.kemitix.s3thorp
+
+
+final case class Counters(uploaded: Int = 0,
+                          deleted: Int = 0,
+                          copied: Int = 0)
diff --git a/src/main/scala/net/kemitix/s3thorp/Exclude.scala b/src/main/scala/net/kemitix/s3thorp/Exclude.scala
index 818dc62..9fa8fc7 100644
--- a/src/main/scala/net/kemitix/s3thorp/Exclude.scala
+++ b/src/main/scala/net/kemitix/s3thorp/Exclude.scala
@@ -4,7 +4,7 @@ import java.nio.file.Path
 import java.util.function.Predicate
 import java.util.regex.Pattern
 
-case class Exclude(exclude: String = "!.*") {
+final case class Exclude(exclude: String = "!.*") {
 
   lazy val predicate: Predicate[String] = Pattern.compile(exclude).asPredicate()
 
diff --git a/src/main/scala/net/kemitix/s3thorp/Filter.scala b/src/main/scala/net/kemitix/s3thorp/Filter.scala
index 17ea823..f27ecab 100644
--- a/src/main/scala/net/kemitix/s3thorp/Filter.scala
+++ b/src/main/scala/net/kemitix/s3thorp/Filter.scala
@@ -4,7 +4,7 @@ import java.nio.file.Path
 import java.util.function.Predicate
 import java.util.regex.Pattern
 
-case class Filter(filter: String = ".*") {
+final case class Filter(filter: String = ".*") {
 
   lazy val predicate: Predicate[String] = Pattern.compile(filter).asPredicate.negate
 
diff --git a/src/main/scala/net/kemitix/s3thorp/LocalFile.scala b/src/main/scala/net/kemitix/s3thorp/LocalFile.scala
index 8c8dd1a..b3a112d 100644
--- a/src/main/scala/net/kemitix/s3thorp/LocalFile.scala
+++ b/src/main/scala/net/kemitix/s3thorp/LocalFile.scala
@@ -3,15 +3,17 @@ package net.kemitix.s3thorp
 import java.io.File
 import java.nio.file.Path
 
-case class LocalFile(file: File,
-                     source: File,
-                     keyGenerator: File => RemoteKey)
-                    (implicit c: Config)
+final case class LocalFile(
+  file: File,
+  source: File,
+  keyGenerator: File => RemoteKey,
+  suppliedHash: Option[MD5Hash] = None)
+  (implicit c: Config)
   extends MD5HashGenerator {
 
   require(!file.isDirectory, s"LocalFile must not be a directory: $file")
 
-  private lazy val myhash = md5File(file)
+  private lazy val myhash = suppliedHash.getOrElse(md5File(file))
 
   def hash: MD5Hash = myhash
 
diff --git a/src/main/scala/net/kemitix/s3thorp/S3Action.scala b/src/main/scala/net/kemitix/s3thorp/S3Action.scala
index 114e5d8..28d42ca 100644
--- a/src/main/scala/net/kemitix/s3thorp/S3Action.scala
+++ b/src/main/scala/net/kemitix/s3thorp/S3Action.scala
@@ -9,22 +9,25 @@ sealed trait S3Action {
 
 }
 
-case class DoNothingS3Action(remoteKey: RemoteKey) extends S3Action {
+final case class DoNothingS3Action(remoteKey: RemoteKey) extends S3Action {
   override val order: Int = 0
 }
 
-case class CopyS3Action(remoteKey: RemoteKey) extends S3Action {
+final case class CopyS3Action(remoteKey: RemoteKey) extends S3Action {
   override val order: Int = 1
 }
-case class UploadS3Action(remoteKey: RemoteKey,
-                          md5Hash: MD5Hash) extends S3Action {
+
+final case class UploadS3Action(
+  remoteKey: RemoteKey,
+  md5Hash: MD5Hash) extends S3Action {
   override val order: Int = 2
 }
-case class DeleteS3Action(remoteKey: RemoteKey) extends S3Action {
+
+final case class DeleteS3Action(remoteKey: RemoteKey) extends S3Action {
   override val order: Int = 3
 }
 
-case class ErroredS3Action(remoteKey: RemoteKey, e: Throwable) extends S3Action {
+final case class ErroredS3Action(remoteKey: RemoteKey, e: Throwable) extends S3Action {
   override val order: Int = 10
 }
 
diff --git a/src/main/scala/net/kemitix/s3thorp/S3MetaData.scala b/src/main/scala/net/kemitix/s3thorp/S3MetaData.scala
index aafd3ef..936988a 100644
--- a/src/main/scala/net/kemitix/s3thorp/S3MetaData.scala
+++ b/src/main/scala/net/kemitix/s3thorp/S3MetaData.scala
@@ -1,6 +1,7 @@
 package net.kemitix.s3thorp
 
 // For the LocalFile, the set of matching S3 objects with the same MD5Hash, and any S3 object with the same remote key
-case class S3MetaData(localFile: LocalFile,
-                      matchByHash: Set[RemoteMetaData],
-                      matchByKey: Option[RemoteMetaData])
\ No newline at end of file
+final case class S3MetaData(
+  localFile: LocalFile,
+  matchByHash: Set[RemoteMetaData],
+  matchByKey: Option[RemoteMetaData])
diff --git a/src/main/scala/net/kemitix/s3thorp/SyncLogging.scala b/src/main/scala/net/kemitix/s3thorp/SyncLogging.scala
index 2f4bc85..459fe1a 100644
--- a/src/main/scala/net/kemitix/s3thorp/SyncLogging.scala
+++ b/src/main/scala/net/kemitix/s3thorp/SyncLogging.scala
@@ -35,8 +35,4 @@ trait SyncLogging extends Logging {
       }
     }
 
-  case class Counters(uploaded: Int = 0,
-                      deleted: Int = 0,
-                      copied: Int = 0)
-
 }
diff --git a/src/main/scala/net/kemitix/s3thorp/awssdk/CancellableMultiPartUpload.scala b/src/main/scala/net/kemitix/s3thorp/awssdk/CancellableMultiPartUpload.scala
index 60eb2bd..b2c9054 100644
--- a/src/main/scala/net/kemitix/s3thorp/awssdk/CancellableMultiPartUpload.scala
+++ b/src/main/scala/net/kemitix/s3thorp/awssdk/CancellableMultiPartUpload.scala
@@ -1,4 +1,5 @@
 package net.kemitix.s3thorp.awssdk
 
-case class CancellableMultiPartUpload(e: Throwable,
-                                      uploadId: String) extends Exception(e)
+final case class CancellableMultiPartUpload(
+  e: Throwable,
+  uploadId: String) extends Exception(e)
diff --git a/src/main/scala/net/kemitix/s3thorp/awssdk/S3ObjectsData.scala b/src/main/scala/net/kemitix/s3thorp/awssdk/S3ObjectsData.scala
index ad5790a..01c6caf 100644
--- a/src/main/scala/net/kemitix/s3thorp/awssdk/S3ObjectsData.scala
+++ b/src/main/scala/net/kemitix/s3thorp/awssdk/S3ObjectsData.scala
@@ -5,7 +5,8 @@ import net.kemitix.s3thorp.{HashModified, KeyModified, MD5Hash, RemoteKey}
 /**
   * A list of objects and their MD5 hash values.
   */
-case class S3ObjectsData(byHash: Map[MD5Hash, Set[KeyModified]],
-                         byKey: Map[RemoteKey, HashModified]) {
+final case class S3ObjectsData(
+  byHash: Map[MD5Hash, Set[KeyModified]],
+  byKey: Map[RemoteKey, HashModified]) {
 
 }
diff --git a/src/test/scala/net/kemitix/s3thorp/UnitTest.scala b/src/test/scala/net/kemitix/s3thorp/UnitTest.scala
index c3a8163..b5caacc 100644
--- a/src/test/scala/net/kemitix/s3thorp/UnitTest.scala
+++ b/src/test/scala/net/kemitix/s3thorp/UnitTest.scala
@@ -8,9 +8,11 @@ abstract class UnitTest extends FunSpec {
 
   def aLocalFile(path: String, myHash: MD5Hash, source: File, fileToKey: File => RemoteKey)
                 (implicit c: Config): LocalFile =
-    new LocalFile(source.toPath.resolve(path).toFile, source, fileToKey) {
-      override def hash: MD5Hash = myHash
-    }
+    LocalFile(
+      file = source.toPath.resolve(path).toFile,
+      source = source,
+      keyGenerator = fileToKey,
+      suppliedHash = Some(myHash))
 
   def aRemoteKey(prefix: RemoteKey, path: String): RemoteKey =
     RemoteKey(prefix.key + "/" + path)