diff --git a/core/src/main/scala/org/apache/spark/BarrierCoordinator.scala b/core/src/main/scala/org/apache/spark/BarrierCoordinator.scala
index 5e546c694e8d9..2e984db5e2f07 100644
--- a/core/src/main/scala/org/apache/spark/BarrierCoordinator.scala
+++ b/core/src/main/scala/org/apache/spark/BarrierCoordinator.scala
@@ -32,7 +32,7 @@ import org.apache.spark.scheduler.{LiveListenerBus, SparkListener, SparkListener
  * we can use (stageId, stageAttemptId) to identify the stage attempt where the barrier() call is
  * from.
  */
-private case class ContextBarrierId(stageId: Int, stageAttemptId: Int) {
+private[spark] case class ContextBarrierId(stageId: Int, stageAttemptId: Int) {
   override def toString: String = s"Stage $stageId (Attempt $stageAttemptId)"
 }
 
@@ -84,13 +84,13 @@ private[spark] class BarrierCoordinator(
 
   /**
    * Provide the current state of a barrier() call. A state is created when a new stage attempt
-   * sends out a barrier() call, and recycled on stage completed.
+   * sends out a barrier() call, and recycled on stage completed. Visible for testing.
    *
    * @param barrierId Identifier of the barrier stage that make a barrier() call.
    * @param numTasks Number of tasks of the barrier stage, all barrier() calls from the stage shall
    *                 collect `numTasks` requests to succeed.
    */
-  private class ContextBarrierState(
+  private[spark] class ContextBarrierState(
       val barrierId: ContextBarrierId,
       val numTasks: Int) {
 
@@ -141,7 +141,7 @@ private[spark] class BarrierCoordinator(
       logInfo(s"Current barrier epoch for $barrierId is $barrierEpoch.")
       if (epoch != barrierEpoch) {
         requester.sendFailure(new SparkException(s"The request to sync of $barrierId with " +
-          s"barrier epoch $barrierEpoch has already finished. Maybe task $taskId is not " +
+          s"barrier epoch $epoch has already finished. Maybe task $taskId is not " +
           "properly killed."))
       } else {
         // If this is the first sync message received for a barrier() call, start timer to ensure
@@ -187,6 +187,12 @@ private[spark] class BarrierCoordinator(
       requesters.clear()
       cancelTimerTask()
     }
+
+    // Check for internal state clear, visible for test only.
+    private[spark] def isInternalStateClear(): Boolean = requesters.isEmpty && timerTask == null
+
+    // Get currently barrier epoch, visible for test only.
+    private[spark] def getBarrierEpoch(): Int = barrierEpoch
   }
 
   // Clean up the [[ContextBarrierState]] that correspond to a specific stage attempt.
@@ -215,7 +221,7 @@ private[spark] class BarrierCoordinator(
   }
 }
 
-private[spark] sealed trait BarrierCoordinatorMessage extends Serializable
+private sealed trait BarrierCoordinatorMessage extends Serializable
 
 /**
  * A global sync request message from BarrierTaskContext, by `barrier()` call. Each request is
diff --git a/core/src/test/scala/org/apache/spark/scheduler/ContextBarrierStateSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/ContextBarrierStateSuite.scala
new file mode 100644
index 0000000000000..af912c84c0dfc
--- /dev/null
+++ b/core/src/test/scala/org/apache/spark/scheduler/ContextBarrierStateSuite.scala
@@ -0,0 +1,175 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.scheduler
+
+import scala.concurrent.duration._
+import scala.language.postfixOps
+
+import org.mockito.ArgumentMatcher
+import org.mockito.Matchers._
+import org.mockito.Mockito._
+import org.scalatest.concurrent.Eventually
+
+import org.apache.spark._
+import org.apache.spark.rpc.{RpcAddress, RpcCallContext, RpcEnv}
+
+class ContextBarrierStateSuite extends SparkFunSuite with LocalSparkContext with Eventually {
+
+  private def mockRpcCallContext() = {
+    val rpcAddress = mock(classOf[RpcAddress])
+    val rpcCallContext = mock(classOf[RpcCallContext])
+    when(rpcCallContext.senderAddress).thenReturn(rpcAddress)
+    rpcCallContext
+  }
+
+  test("normal test for single task") {
+    val barrierCoordinator = new BarrierCoordinator(
+      5, mock(classOf[LiveListenerBus]), mock(classOf[RpcEnv]))
+    val stageId = 0
+    val stageAttemptNumber = 0
+    val state = new barrierCoordinator.ContextBarrierState(
+      ContextBarrierId(stageId, stageAttemptNumber), numTasks = 1)
+    state.handleRequest(
+      mockRpcCallContext(),
+      RequestToSync(
+        numTasks = 1,
+        stageId,
+        stageAttemptNumber,
+        taskAttemptId = 0,
+        barrierEpoch = 0))
+    // Ensure barrierEpoch value have been changed.
+    assert(state.getBarrierEpoch() == 1)
+    assert(state.isInternalStateClear())
+  }
+
+  test("normal test for multi tasks") {
+    val barrierCoordinator = new BarrierCoordinator(
+      5, mock(classOf[LiveListenerBus]), mock(classOf[RpcEnv]))
+    val numTasks = 3
+    val stageId = 0
+    val stageAttemptNumber = 0
+    val state = new barrierCoordinator.ContextBarrierState(
+      ContextBarrierId(stageId, stageAttemptNumber), numTasks)
+    // request from 3 tasks
+    (0 until numTasks).foreach { taskId =>
+      state.handleRequest(mockRpcCallContext(), RequestToSync(
+        numTasks,
+        stageId,
+        stageAttemptNumber,
+        taskAttemptId = taskId,
+        barrierEpoch = 0))
+    }
+    // Ensure barrierEpoch value have been changed.
+    assert(state.getBarrierEpoch() == 1)
+    assert(state.isInternalStateClear())
+  }
+
+  test("abnormal test for syncing with illegal barrierId") {
+    val barrierCoordinator = new BarrierCoordinator(
+      5, mock(classOf[LiveListenerBus]), mock(classOf[RpcEnv]))
+    val numTasks = 3
+    val stageId = 0
+    val stageAttemptNumber = 0
+    val rpcCallContext = mockRpcCallContext()
+    val state = new barrierCoordinator.ContextBarrierState(
+      ContextBarrierId(stageId, stageAttemptNumber), numTasks)
+    state.handleRequest(
+      rpcCallContext,
+      RequestToSync(
+        numTasks,
+        stageId,
+        stageAttemptNumber,
+        taskAttemptId = 0,
+        barrierEpoch = -1))
+    verify(rpcCallContext, times(1))
+      .sendFailure(argThat(new ArgumentMatcher[SparkException] {
+        override def matches(e: Any): Boolean = {
+          e.asInstanceOf[SparkException].getMessage ==
+            "The request to sync of Stage 0 (Attempt 0) with barrier epoch -1 has already" +
+              " finished. Maybe task 0 is not properly killed."
+        }
+      }))
+  }
+
+  test("abnormal test for syncing with old barrierId") {
+    val barrierCoordinator = new BarrierCoordinator(
+      5, mock(classOf[LiveListenerBus]), mock(classOf[RpcEnv]))
+    val numTasks = 3
+    val stageId = 0
+    val stageAttemptNumber = 0
+    val rpcCallContext = mockRpcCallContext()
+    val state = new barrierCoordinator.ContextBarrierState(
+      ContextBarrierId(stageId, stageAttemptNumber), numTasks)
+    // request from 3 tasks
+    (0 until numTasks).foreach { taskId =>
+      state.handleRequest(
+        rpcCallContext,
+        RequestToSync(
+          numTasks,
+          stageId,
+          stageAttemptNumber,
+          taskAttemptId = taskId,
+          barrierEpoch = 0))
+    }
+    // Ensure barrierEpoch value have been changed.
+    assert(state.getBarrierEpoch() == 1)
+    assert(state.isInternalStateClear())
+    state.handleRequest(
+      rpcCallContext,
+      RequestToSync(
+        numTasks,
+        stageId,
+        stageAttemptNumber,
+        taskAttemptId = 0,
+        barrierEpoch = 0))
+    verify(rpcCallContext, times(1))
+      .sendFailure(argThat(new ArgumentMatcher[SparkException] {
+        override def matches(e: Any): Boolean = {
+          e.asInstanceOf[SparkException].getMessage ==
+            "The request to sync of Stage 0 (Attempt 0) with barrier epoch 0 has already" +
+              " finished. Maybe task 0 is not properly killed."
+        }}))
+  }
+
+  test("abnormal test for timeout when rpcTimeOut > barrierTimeOut") {
+    val barrierCoordinator = new BarrierCoordinator(
+      2, mock(classOf[LiveListenerBus]), mock(classOf[RpcEnv]))
+    val numTasks = 3
+    val stageId = 0
+    val stageAttemptNumber = 0
+    val rpcCallContext = mockRpcCallContext()
+    val state = new barrierCoordinator.ContextBarrierState(
+      ContextBarrierId(stageId, stageAttemptNumber), numTasks)
+    state.handleRequest(rpcCallContext, RequestToSync(
+      numTasks,
+      stageId,
+      stageAttemptNumber,
+      taskAttemptId = 0,
+      barrierEpoch = 0))
+    eventually(timeout(5.seconds)) {
+      verify(rpcCallContext, times(1))
+        .sendFailure(argThat(new ArgumentMatcher[SparkException] {
+          override def matches(e: Any): Boolean = {
+            e.asInstanceOf[SparkException].getMessage ==
+              "The coordinator didn't get all barrier sync requests for barrier epoch" +
+                " 0 from Stage 0 (Attempt 0) within 2 second(s)."
+          }
+        }))
+    }
+  }
+}