diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index 19e0c441964..204715631af 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -366,6 +366,9 @@ Release 2.3.0 - UNRELEASED
     HDFS-5276. FileSystem.Statistics should use thread-local counters to avoid
     multi-threaded performance issues on read/write.  (Colin Patrick McCabe)
 
+    HADOOP-9291. enhance unit-test coverage of package o.a.h.metrics2 (Ivan A.
+    Veselovsky via jeagles)
+
   OPTIMIZATIONS
 
     HADOOP-9748. Reduce blocking on UGI.ensureInitialized (daryn)
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/filter/AbstractPatternFilter.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/filter/AbstractPatternFilter.java
index 1f779735a59..07b50ab9774 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/filter/AbstractPatternFilter.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/filter/AbstractPatternFilter.java
@@ -112,7 +112,7 @@ public abstract class AbstractPatternFilter extends MetricsFilter {
       return false;
     }
     // Reject if no match in whitelist only mode
-    if (ipat != null && epat == null) {
+    if (!includeTagPatterns.isEmpty() && excludeTagPatterns.isEmpty()) {
       return false;
     }
     return true;
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/package-info.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/package-info.java
index 2f787d04492..be2149977cd 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/package-info.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/package-info.java
@@ -234,7 +234,7 @@
     patterns.
   </p>
   <p>Similarly, you can specify the <code>record.filter</code> and
-    <code>metrics.filter</code> options, which operate at record and metric
+    <code>metric.filter</code> options, which operate at record and metric
     level, respectively. Filters can be combined to optimize
     the filtering efficiency.</p>
 
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/filter/TestPatternFilter.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/filter/TestPatternFilter.java
index 2bdfdb978a9..a8f38d6136b 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/filter/TestPatternFilter.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/filter/TestPatternFilter.java
@@ -23,9 +23,11 @@ import java.util.List;
 
 import org.apache.commons.configuration.SubsetConfiguration;
 import org.junit.Test;
+
 import static org.junit.Assert.*;
 import static org.mockito.Mockito.*;
 
+import org.apache.hadoop.metrics2.MetricsFilter;
 import org.apache.hadoop.metrics2.MetricsRecord;
 import org.apache.hadoop.metrics2.MetricsTag;
 import org.apache.hadoop.metrics2.impl.ConfigBuilder;
@@ -53,7 +55,7 @@ public class TestPatternFilter {
         .add("p.include.tags", "foo:f").subset("p");
     shouldAccept(wl, "foo");
     shouldAccept(wl, Arrays.asList(tag("bar", "", ""),
-                                   tag("foo", "", "f")));
+                                   tag("foo", "", "f")), new boolean[] {false, true});
     shouldAccept(wl, mockMetricsRecord("foo", Arrays.asList(
       tag("bar", "", ""), tag("foo", "", "f"))));
     shouldReject(wl, "bar");
@@ -78,7 +80,7 @@ public class TestPatternFilter {
       tag("bar", "", ""))));
     shouldReject(bl, "foo");
     shouldReject(bl, Arrays.asList(tag("bar", "", ""),
-                                   tag("foo", "", "f")));
+                                   tag("foo", "", "f")), new boolean[] {true, false});
     shouldReject(bl, mockMetricsRecord("foo", Arrays.asList(
       tag("bar", "", ""))));
     shouldReject(bl, mockMetricsRecord("bar", Arrays.asList(
@@ -125,15 +127,61 @@ public class TestPatternFilter {
     shouldAccept(c, mockMetricsRecord("foo", Arrays.asList(
       tag("foo", "", "f"))));
   }
-
+  
   static void shouldAccept(SubsetConfiguration conf, String s) {
     assertTrue("accepts "+ s, newGlobFilter(conf).accepts(s));
     assertTrue("accepts "+ s, newRegexFilter(conf).accepts(s));
   }
 
+  // Version for one tag:
   static void shouldAccept(SubsetConfiguration conf, List<MetricsTag> tags) {
-    assertTrue("accepts "+ tags, newGlobFilter(conf).accepts(tags));
-    assertTrue("accepts "+ tags, newRegexFilter(conf).accepts(tags));
+    shouldAcceptImpl(true, conf, tags, new boolean[] {true});
+  }
+  // Version for multiple tags: 
+  static void shouldAccept(SubsetConfiguration conf, List<MetricsTag> tags, 
+      boolean[] expectedAcceptedSpec) {
+    shouldAcceptImpl(true, conf, tags, expectedAcceptedSpec);
+  }
+
+  // Version for one tag:
+  static void shouldReject(SubsetConfiguration conf, List<MetricsTag> tags) {
+    shouldAcceptImpl(false, conf, tags, new boolean[] {false});
+  }
+  // Version for multiple tags: 
+  static void shouldReject(SubsetConfiguration conf, List<MetricsTag> tags, 
+      boolean[] expectedAcceptedSpec) {
+    shouldAcceptImpl(false, conf, tags, expectedAcceptedSpec);
+  }
+  
+  private static void shouldAcceptImpl(final boolean expectAcceptList,  
+      SubsetConfiguration conf, List<MetricsTag> tags, boolean[] expectedAcceptedSpec) {
+    final MetricsFilter globFilter = newGlobFilter(conf);
+    final MetricsFilter regexFilter = newRegexFilter(conf);
+    
+    // Test acceptance of the tag list:  
+    assertEquals("accepts "+ tags, expectAcceptList, globFilter.accepts(tags));
+    assertEquals("accepts "+ tags, expectAcceptList, regexFilter.accepts(tags));
+    
+    // Test results on each of the individual tags:
+    int acceptedCount = 0;
+    for (int i=0; i<tags.size(); i++) {
+      MetricsTag tag = tags.get(i);
+      boolean actGlob = globFilter.accepts(tag);
+      boolean actRegex = regexFilter.accepts(tag);
+      assertEquals("accepts "+tag, expectedAcceptedSpec[i], actGlob);
+      // Both the filters should give the same result:
+      assertEquals(actGlob, actRegex);
+      if (actGlob) {
+        acceptedCount++;
+      }
+    }
+    if (expectAcceptList) {
+      // At least one individual tag should be accepted:
+      assertTrue("No tag of the following accepted: " + tags, acceptedCount > 0);
+    } else {
+      // At least one individual tag should be rejected: 
+      assertTrue("No tag of the following rejected: " + tags, acceptedCount < tags.size());
+    }
   }
 
   /**
@@ -152,11 +200,6 @@ public class TestPatternFilter {
     assertTrue("rejects "+ s, !newRegexFilter(conf).accepts(s));
   }
 
-  static void shouldReject(SubsetConfiguration conf, List<MetricsTag> tags) {
-    assertTrue("rejects "+ tags, !newGlobFilter(conf).accepts(tags));
-    assertTrue("rejects "+ tags, !newRegexFilter(conf).accepts(tags));
-  }
-
   /**
    * Asserts that filters with the given configuration reject the given record.
    * 
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/sink/TestFileSink.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/sink/TestFileSink.java
new file mode 100644
index 00000000000..8c918b8431b
--- /dev/null
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/sink/TestFileSink.java
@@ -0,0 +1,138 @@
+/*
+ * 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.metrics2.sink;
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.regex.Pattern;
+
+import org.apache.hadoop.io.IOUtils;
+import org.apache.hadoop.metrics2.MetricsSystem;
+import org.apache.hadoop.metrics2.annotation.Metric;
+import org.apache.hadoop.metrics2.annotation.Metrics;
+import org.apache.hadoop.metrics2.annotation.Metric.Type;
+import org.apache.hadoop.metrics2.impl.ConfigBuilder;
+import org.apache.hadoop.metrics2.impl.MetricsSystemImpl;
+import org.apache.hadoop.metrics2.impl.TestMetricsConfig;
+import org.apache.hadoop.metrics2.lib.MutableGaugeInt;
+import org.junit.After;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+public class TestFileSink {
+  
+  private File outFile;
+
+  // The 2 sample metric classes:
+  @Metrics(name="testRecord1", context="test1")
+  static class MyMetrics1 {
+    @Metric(value={"testTag1", ""}, type=Type.TAG) 
+    String testTag1() { return "testTagValue1"; }
+    
+    @Metric(value={"testTag2", ""}, type=Type.TAG) 
+    String gettestTag2() { return "testTagValue2"; }
+    
+    @Metric(value={"testMetric1", "An integer gauge"},always=true) 
+    MutableGaugeInt testMetric1;
+    
+    @Metric(value={"testMetric2", "An integer gauge"},always=true) 
+    MutableGaugeInt testMetric2;
+
+    public MyMetrics1 registerWith(MetricsSystem ms) {
+      return ms.register("m1", null, this);
+    }
+  }
+  
+  @Metrics(name="testRecord2", context="test1")
+  static class MyMetrics2 {
+    @Metric(value={"testTag22", ""}, type=Type.TAG) 
+    String testTag1() { return "testTagValue22"; }
+
+    public MyMetrics2 registerWith(MetricsSystem ms) {
+      return ms.register("m2", null, this);
+    }
+  }
+  
+  private File getTestTempFile(String prefix, String suffix) throws IOException {
+    String tmpPath = System.getProperty("java.io.tmpdir", "/tmp");
+    String user = System.getProperty("user.name", "unknown-user");
+    File dir = new File(tmpPath + "/" + user);
+    dir.mkdirs();
+    return File.createTempFile(prefix, suffix, dir);
+  }
+  
+  @Test(timeout=6000) 
+  public void testFileSink() throws IOException {
+    outFile = getTestTempFile("test-file-sink-", ".out");
+    final String outPath = outFile.getAbsolutePath();  
+    
+    // NB: specify large period to avoid multiple metrics snapshotting: 
+    new ConfigBuilder().add("*.period", 10000)
+        .add("test.sink.mysink0.class", FileSink.class.getName())
+        .add("test.sink.mysink0.filename", outPath)
+        // NB: we filter by context to exclude "metricssystem" context metrics:
+        .add("test.sink.mysink0.context", "test1")
+        .save(TestMetricsConfig.getTestFilename("hadoop-metrics2-test"));
+    MetricsSystemImpl ms = new MetricsSystemImpl("test");
+    ms.start();
+
+    final MyMetrics1 mm1 
+      = new MyMetrics1().registerWith(ms);
+    new MyMetrics2().registerWith(ms);
+
+    mm1.testMetric1.incr();
+    mm1.testMetric2.incr(2);
+
+    ms.publishMetricsNow(); // publish the metrics
+    ms.stop();
+    ms.shutdown();
+    
+    InputStream is = new FileInputStream(outFile);
+    ByteArrayOutputStream baos = new ByteArrayOutputStream((int)outFile.length());
+    IOUtils.copyBytes(is, baos, 1024, true);
+    String outFileContent = new String(baos.toByteArray(), "UTF-8");
+
+    // Check the out file content. Should be something like the following:
+    //1360244820087 test1.testRecord1: Context=test1, testTag1=testTagValue1, testTag2=testTagValue2, Hostname=myhost, testMetric1=1, testMetric2=2
+    //1360244820089 test1.testRecord2: Context=test1, testTag22=testTagValue22, Hostname=myhost
+    
+    // Note that in the below expression we allow tags and metrics to go in arbitrary order.  
+    Pattern expectedContentPattern = Pattern.compile(
+        // line #1:
+        "^\\d+\\s+test1.testRecord1:\\s+Context=test1,\\s+" +
+        "(testTag1=testTagValue1,\\s+testTag2=testTagValue2|testTag2=testTagValue2,\\s+testTag1=testTagValue1)," +
+        "\\s+Hostname=.*,\\s+(testMetric1=1,\\s+testMetric2=2|testMetric2=2,\\s+testMetric1=1)" +
+        // line #2:
+        "$[\\n\\r]*^\\d+\\s+test1.testRecord2:\\s+Context=test1," +
+        "\\s+testTag22=testTagValue22,\\s+Hostname=.*$[\\n\\r]*", 
+         Pattern.MULTILINE);
+     assertTrue(expectedContentPattern.matcher(outFileContent).matches());
+  }
+  
+  @After
+  public void after() {
+    if (outFile != null) {
+      outFile.delete();
+      assertTrue(!outFile.exists());
+    }
+  }
+}