diff --git a/cluster-sharding/src/main/scala/com/evolutiongaming/akkaeffect/cluster/sharding/ClusterShardingLocal.scala b/cluster-sharding/src/main/scala/com/evolutiongaming/akkaeffect/cluster/sharding/ClusterShardingLocal.scala
index cb155b3d..8eac0eb6 100644
--- a/cluster-sharding/src/main/scala/com/evolutiongaming/akkaeffect/cluster/sharding/ClusterShardingLocal.scala
+++ b/cluster-sharding/src/main/scala/com/evolutiongaming/akkaeffect/cluster/sharding/ClusterShardingLocal.scala
@@ -19,11 +19,17 @@ import scala.concurrent.Promise
 import scala.concurrent.duration._
 import scala.util.Try
 
-
+/** Stub for [[ClusterSharding]] to be used in the unit tests. */
 trait ClusterShardingLocal[F[_]] {
 
+  /** Provides the actual stub */
   def clusterSharding: ClusterSharding[F]
 
+  /** Simulate cluster rebalacing.
+    *
+    * I.e. send `handOffStopMessage` from [[ClusterSharding#startProxy]] to the
+    * actors that need rebalancing according to `shardAllocationStrategy`.
+    */
   def rebalance: F[Unit]
 }
 
diff --git a/cluster/src/main/scala/com/evolutiongaming/akkaeffect/cluster/DataCenter.scala b/cluster/src/main/scala/com/evolutiongaming/akkaeffect/cluster/DataCenter.scala
index 264b67e4..f30ebeaa 100644
--- a/cluster/src/main/scala/com/evolutiongaming/akkaeffect/cluster/DataCenter.scala
+++ b/cluster/src/main/scala/com/evolutiongaming/akkaeffect/cluster/DataCenter.scala
@@ -3,7 +3,7 @@ package com.evolutiongaming.akkaeffect.cluster
 import cats.{Order, Show}
 import pureconfig.ConfigReader
 
-
+/** Datacenter where required cluster singletons are located */
 final case class DataCenter(value: String) {
 
   override def toString: String = value
@@ -16,4 +16,4 @@ object DataCenter {
   implicit val showDataCenter: Show[DataCenter] = Show.fromToString
 
   implicit val configReaderDataCenter: ConfigReader[DataCenter] = ConfigReader[String].map { a => DataCenter(a) }
-}
\ No newline at end of file
+}