diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestUnderReplicatedBlockQueues.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestUnderReplicatedBlockQueues.java
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+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestUnderReplicatedBlockQueues.java
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+/**
+ * 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.hadoop.hdfs.server.blockmanagement;
+
+import org.apache.hadoop.hdfs.protocol.Block;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class TestUnderReplicatedBlockQueues extends Assert {
+
+  /**
+   * Test that adding blocks with different replication counts puts them
+   * into different queues
+   * @throws Throwable if something goes wrong
+   */
+  @Test
+  public void testBlockPriorities() throws Throwable {
+    UnderReplicatedBlocks queues = new UnderReplicatedBlocks();
+    Block block1 = new Block(1);
+    Block block2 = new Block(2);
+    Block block_very_under_replicated = new Block(3);
+    Block block_corrupt = new Block(4);
+
+    //add a block with a single entry
+    assertAdded(queues, block1, 1, 0, 3);
+
+    assertEquals(1, queues.getUnderReplicatedBlockCount());
+    assertEquals(1, queues.size());
+    assertInLevel(queues, block1, UnderReplicatedBlocks.QUEUE_HIGHEST_PRIORITY);
+    //repeated additions fail
+    assertFalse(queues.add(block1, 1, 0, 3));
+
+    //add a second block with two replicas
+    assertAdded(queues, block2, 2, 0, 3);
+    assertEquals(2, queues.getUnderReplicatedBlockCount());
+    assertEquals(2, queues.size());
+    assertInLevel(queues, block2, UnderReplicatedBlocks.QUEUE_UNDER_REPLICATED);
+    //now try to add a block that is corrupt
+    assertAdded(queues, block_corrupt, 0, 0, 3);
+    assertEquals(3, queues.size());
+    assertEquals(2, queues.getUnderReplicatedBlockCount());
+    assertEquals(1, queues.getCorruptBlockSize());
+    assertInLevel(queues, block_corrupt,
+                  UnderReplicatedBlocks.QUEUE_WITH_CORRUPT_BLOCKS);
+
+    //insert a very under-replicated block
+    assertAdded(queues, block_very_under_replicated, 4, 0, 25);
+    assertInLevel(queues, block_very_under_replicated,
+                  UnderReplicatedBlocks.QUEUE_VERY_UNDER_REPLICATED);
+
+  }
+
+  private void assertAdded(UnderReplicatedBlocks queues,
+                           Block block,
+                           int curReplicas,
+                           int decomissionedReplicas,
+                           int expectedReplicas) {
+    assertTrue("Failed to add " + block,
+               queues.add(block,
+                          curReplicas,
+                          decomissionedReplicas,
+                          expectedReplicas));
+  }
+
+  /**
+   * Determine whether or not a block is in a level without changing the API.
+   * Instead get the per-level iterator and run though it looking for a match.
+   * If the block is not found, an assertion is thrown.
+   *
+   * This is inefficient, but this is only a test case.
+   * @param queues queues to scan
+   * @param block block to look for
+   * @param level level to select
+   */
+  private void assertInLevel(UnderReplicatedBlocks queues,
+                             Block block,
+                             int level) {
+    UnderReplicatedBlocks.BlockIterator bi = queues.iterator(level);
+    while (bi.hasNext()) {
+      Block next = bi.next();
+      if (block.equals(next)) {
+        return;
+      }
+    }
+    fail("Block " + block + " not found in level " + level);
+  }
+}