Add ExtractAppender to facilite junit tests

Added ExtractAppender to provide a way for junit tests to capture
data sent to a logger.
Changed logback.version to 1.2.3 and moved the property to the
top-level pom.
Updated license date in top-level pom.
Refactored ExceptionsText, adding ErrorsTester and
ThrowablesTester classes to reduce sonar issues.

Change-Id: Ief7d08972bf4e7037b59c2afe4b77b252f2ad60a
Issue-ID: POLICY-582
Signed-off-by: Jim Hahn <jrh3@att.com>

5 files changed, 820 insertions, 104 deletions

diff --git a/utils-test/src/test/java/org/onap/policy/common/utils/test/ConstructionErrorTest.java b/utils-test/src/test/java/org/onap/policy/common/utils/test/ConstructionErrorTest.java
new file mode 100644
index 00000000..4a6cd90e
--- /dev/null
+++ b/utils-test/src/test/java/org/onap/policy/common/utils/test/ConstructionErrorTest.java
@@ -0,0 +1,37 @@
+/*
+ * ============LICENSE_START=======================================================
+ * Integrity Audit
+ * ================================================================================
+ * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.utils.test;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+/**
+ * 
+ */
+public class ConstructionErrorTest extends ErrorsTester {
+
+	@Test
+	public void test() throws Exception {
+		assertEquals(4, testError(ConstructionError.class));
+	}
+
+}
diff --git a/utils-test/src/test/java/org/onap/policy/common/utils/test/ErrorsTesterTest.java b/utils-test/src/test/java/org/onap/policy/common/utils/test/ErrorsTesterTest.java
new file mode 100644
index 00000000..ae684d52
--- /dev/null
+++ b/utils-test/src/test/java/org/onap/policy/common/utils/test/ErrorsTesterTest.java
@@ -0,0 +1,77 @@
+/*
+ * ============LICENSE_START=======================================================
+ * Integrity Monitor
+ * ================================================================================
+ * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.utils.test;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class ErrorsTesterTest {
+
+	@Test
+	public void test() {
+		assertEquals(2, new ErrorsTester().testError(SimpleError.class));
+		assertEquals(5, new ErrorsTester().testError(StaticError.class));
+	}
+
+	/**
+	 * Used to test a simple success case.
+	 */
+	public static class SimpleError extends Error {
+		private static final long serialVersionUID = 1L;
+
+		public SimpleError() {
+			super();
+		}
+
+		public SimpleError(String message) {
+			super(message);
+		}
+	}
+
+	/**
+	 * Used to test the exhaustive success case.
+	 */
+	public static class StaticError extends Error {
+		private static final long serialVersionUID = 1L;
+
+		public StaticError() {
+			super();
+		}
+
+		public StaticError(String message) {
+			super(message);
+		}
+
+		public StaticError(Throwable cause) {
+			super(cause);
+		}
+
+		public StaticError(String message, Throwable cause) {
+			super(message, cause);
+		}
+
+		public StaticError(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
+			super(message, cause, enableSuppression, writableStackTrace);
+		}
+	}
+
+}
diff --git a/utils-test/src/test/java/org/onap/policy/common/utils/test/ExceptionsTesterTest.java b/utils-test/src/test/java/org/onap/policy/common/utils/test/ExceptionsTesterTest.java
index c6af77a2..3848acd0 100644
--- a/utils-test/src/test/java/org/onap/policy/common/utils/test/ExceptionsTesterTest.java
+++ b/utils-test/src/test/java/org/onap/policy/common/utils/test/ExceptionsTesterTest.java
@@ -27,124 +27,26 @@ import org.junit.Test;
 public class ExceptionsTesterTest {
 
 	@Test
-	public void test() throws Exception {
+	public void test() {
 		assertEquals(2, new ExceptionsTester().test(SimpleException.class));
 		assertEquals(8, new ExceptionsTester().test(StaticException.class));
 	}
 
 	@Test(expected = AssertionError.class)
-	public void testIgnoreMessageException() throws Exception {
-		new ExceptionsTester().test(IgnoreMessageException.class);
-	}
-
-	@Test(expected = AssertionError.class)
-	public void testIgnoreCauseException() throws Exception {
-		new ExceptionsTester().test(IgnoreCauseException.class);
-	}
-
-	@Test(expected = AssertionError.class)
-	public void testNonStaticException() throws Exception {
+	public void testNoConstructorsException() {
 		new ExceptionsTester().test(NoConstructorsException.class);
 	}
 
-	@Test(expected = AssertionError.class)
-	public void testAlwaysSuppressException() throws Exception {
-		new ExceptionsTester().test(AlwaysSuppressException.class);
-	}
-
-	@Test(expected = AssertionError.class)
-	public void testNeverSuppressException() throws Exception {
-		new ExceptionsTester().test(NeverSuppressException.class);
-	}
-
-	@Test(expected = AssertionError.class)
-	public void testAlwaysWritableException() throws Exception {
-		new ExceptionsTester().test(AlwaysWritableException.class);
-	}
-
-	@Test(expected = AssertionError.class)
-	public void testNeverWritableException() throws Exception {
-		new ExceptionsTester().test(NeverWritableException.class);
-	}
-
 	/**
-	 * Used to test a failure case - message text is ignored.
-	 */
-	public static class IgnoreMessageException extends Exception {
-		private static final long serialVersionUID = 1L;
-
-		public IgnoreMessageException(String message) {
-			super("bogus");
-		}
-	}
-
-	/**
-	 * Used to test a failure case - cause is ignored.
-	 */
-	public static class IgnoreCauseException extends Exception {
-		private static final long serialVersionUID = 1L;
-
-		public IgnoreCauseException(Throwable cause) {
-			super(new Exception("another cause"));
-		}
-	}
-
-	/**
-	 * Used to test a failure case - this has no standard constructions.
+	 * Used to test a failure case - this has no standard constructors. The only
+	 * constructor it has takes an "int", thus it is not one of the standard
+	 * constructors.
 	 */
 	public static class NoConstructorsException extends Exception {
 		private static final long serialVersionUID = 1L;
 
 		public NoConstructorsException(int value) {
-			super(String.valueOf(value));
-		}
-	}
-
-	/**
-	 * Used to test a failure case - always suppresses.
-	 */
-	public static class AlwaysSuppressException extends Exception {
-		private static final long serialVersionUID = 1L;
-
-		public AlwaysSuppressException(String message, Throwable cause, boolean enableSuppression,
-				boolean writableStackTrace) {
-			super(message, cause, true, writableStackTrace);
-		}
-	}
-
-	/**
-	 * Used to test a failure case - never suppresses.
-	 */
-	public static class NeverSuppressException extends Exception {
-		private static final long serialVersionUID = 1L;
-
-		public NeverSuppressException(String message, Throwable cause, boolean enableSuppression,
-				boolean writableStackTrace) {
-			super(message, cause, false, writableStackTrace);
-		}
-	}
-
-	/**
-	 * Used to test a failure case - always allows stack writes.
-	 */
-	public static class AlwaysWritableException extends Exception {
-		private static final long serialVersionUID = 1L;
-
-		public AlwaysWritableException(String message, Throwable cause, boolean enableSuppression,
-				boolean writableStackTrace) {
-			super(message, cause, enableSuppression, true);
-		}
-	}
-
-	/**
-	 * Used to test a failure case - never allows stack writes.
-	 */
-	public static class NeverWritableException extends Exception {
-		private static final long serialVersionUID = 1L;
-
-		public NeverWritableException(String message, Throwable cause, boolean enableSuppression,
-				boolean writableStackTrace) {
-			super(message, cause, enableSuppression, false);
+			super();
 		}
 	}
 
diff --git a/utils-test/src/test/java/org/onap/policy/common/utils/test/ThrowablesTesterTest.java b/utils-test/src/test/java/org/onap/policy/common/utils/test/ThrowablesTesterTest.java
new file mode 100644
index 00000000..cb96e98f
--- /dev/null
+++ b/utils-test/src/test/java/org/onap/policy/common/utils/test/ThrowablesTesterTest.java
@@ -0,0 +1,216 @@
+/*
+ * ============LICENSE_START=======================================================
+ * Integrity Monitor
+ * ================================================================================
+ * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.utils.test;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class ThrowablesTesterTest {
+
+	@Test
+	public void test() {
+		assertEquals(2, new ThrowablesTester().testThrowable(SimpleThrowable.class));
+		assertEquals(5, new ThrowablesTester().testThrowable(StaticThrowable.class));
+	}
+
+	@Test
+	public void testNoConstructorsThrowable() {
+		// this will not throw an error, but it should return 0, as there are
+		// no matching constructors
+		assertEquals(0, new ThrowablesTester().testThrowable(NoConstructorsThrowable.class));
+	}
+
+	@Test(expected = AssertionError.class)
+	public void testIgnoreMessageThrowable() {
+		new ThrowablesTester().testThrowable(IgnoreMessageThrowable.class);
+	}
+
+	@Test(expected = AssertionError.class)
+	public void testIgnoreCauseThrowable() {
+		new ThrowablesTester().testThrowable(IgnoreCauseThrowable.class);
+	}
+
+	@Test(expected = AssertionError.class)
+	public void testAlwaysSuppressThrowable() {
+		new ThrowablesTester().testThrowable(AlwaysSuppressThrowable.class);
+	}
+
+	@Test(expected = AssertionError.class)
+	public void testNeverSuppressThrowable() {
+		new ThrowablesTester().testThrowable(NeverSuppressThrowable.class);
+	}
+
+	@Test(expected = AssertionError.class)
+	public void testAlwaysWritableThrowable() {
+		new ThrowablesTester().testThrowable(AlwaysWritableThrowable.class);
+	}
+
+	@Test(expected = AssertionError.class)
+	public void testNeverWritableThrowable() {
+		new ThrowablesTester().testThrowable(NeverWritableThrowable.class);
+	}
+
+	@Test(expected = ConstructionError.class)
+	public void testThrowInstantiationException() {
+		new ThrowablesTester().testThrowable(ThrowInstantiationException.class);
+	}
+
+	/**
+	 * Used to test a failure case - message text is ignored.
+	 */
+	public static class IgnoreMessageThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public IgnoreMessageThrowable(String message) {
+			super("bogus");
+		}
+	}
+
+	/**
+	 * Used to test a failure case - cause is ignored.
+	 */
+	public static class IgnoreCauseThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public IgnoreCauseThrowable(Throwable cause) {
+			super(new Throwable("another cause"));
+		}
+	}
+
+	/**
+	 * Used to test a failure case - this has no standard constructors. The only
+	 * constructor it has takes an "int", thus it is not one of the standard
+	 * constructors.
+	 */
+	public static class NoConstructorsThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public NoConstructorsThrowable(int value) {
+			super();
+		}
+	}
+
+	/**
+	 * Used to test a failure case - always suppresses.
+	 */
+	public static class AlwaysSuppressThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public AlwaysSuppressThrowable(String message, Throwable cause, boolean enableSuppression,
+				boolean writableStackTrace) {
+			super(message, cause, true, writableStackTrace);
+		}
+	}
+
+	/**
+	 * Used to test a failure case - never suppresses.
+	 */
+	public static class NeverSuppressThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public NeverSuppressThrowable(String message, Throwable cause, boolean enableSuppression,
+				boolean writableStackTrace) {
+			super(message, cause, false, writableStackTrace);
+		}
+	}
+
+	/**
+	 * Used to test a failure case - always allows stack writes.
+	 */
+	public static class AlwaysWritableThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public AlwaysWritableThrowable(String message, Throwable cause, boolean enableSuppression,
+				boolean writableStackTrace) {
+			super(message, cause, enableSuppression, true);
+		}
+	}
+
+	/**
+	 * Used to test a failure case - never allows stack writes.
+	 */
+	public static class NeverWritableThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public NeverWritableThrowable(String message, Throwable cause, boolean enableSuppression,
+				boolean writableStackTrace) {
+			super(message, cause, enableSuppression, false);
+		}
+	}
+
+	/**
+	 * Used to test a failure case - throws InstantiationException when
+	 * constructed.
+	 */
+	public static class ThrowInstantiationException extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public ThrowInstantiationException(String message, Throwable cause, boolean enableSuppression,
+				boolean writableStackTrace) throws InstantiationException {
+
+			throw new InstantiationException(ThrowablesTester.EXPECTED_EXCEPTION_MSG);
+		}
+	}
+
+	/**
+	 * Used to test a simple success case.
+	 */
+	public static class SimpleThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public SimpleThrowable() {
+			super();
+		}
+
+		public SimpleThrowable(String message) {
+			super(message);
+		}
+	}
+
+	/**
+	 * Used to test the exhaustive success case.
+	 */
+	public static class StaticThrowable extends Throwable {
+		private static final long serialVersionUID = 1L;
+
+		public StaticThrowable() {
+			super();
+		}
+
+		public StaticThrowable(String message) {
+			super(message);
+		}
+
+		public StaticThrowable(Throwable cause) {
+			super(cause);
+		}
+
+		public StaticThrowable(String message, Throwable cause) {
+			super(message, cause);
+		}
+
+		public StaticThrowable(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
+			super(message, cause, enableSuppression, writableStackTrace);
+		}
+	}
+
+}
diff --git a/utils-test/src/test/java/org/onap/policy/common/utils/test/log/logback/ExtractAppenderTest.java b/utils-test/src/test/java/org/onap/policy/common/utils/test/log/logback/ExtractAppenderTest.java
new file mode 100644
index 00000000..a9a69252
--- /dev/null
+++ b/utils-test/src/test/java/org/onap/policy/common/utils/test/log/logback/ExtractAppenderTest.java
@@ -0,0 +1,484 @@
+/*
+ * ============LICENSE_START=======================================================
+ * Integrity Audit
+ * ================================================================================
+ * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * Licensed 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.utils.test.log.logback;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.slf4j.LoggerFactory;
+
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.Logger;
+import ch.qos.logback.classic.spi.ILoggingEvent;
+
+public class ExtractAppenderTest {
+
+	/**
+	 * Milliseconds to wait for a thread to terminate.
+	 */
+	private static final long THREAD_WAIT_MS = 5000l;
+
+	private static Logger logger;
+
+	private List<Thread> threads;
+
+	@BeforeClass
+	public static void setUpBeforeClass() throws Exception {
+		logger = (Logger) LoggerFactory.getLogger(ExtractAppenderTest.class);
+		logger.setLevel(Level.INFO);
+	}
+
+	@Before
+	public void setUp() throws Exception {
+		threads = new LinkedList<>();
+	}
+
+	@After
+	public void tearDown() throws Exception {
+		logger.detachAndStopAllAppenders();
+
+		for (Thread p : threads) {
+			p.interrupt();
+			p.join(THREAD_WAIT_MS);
+		}
+	}
+
+	@Test
+	public void testExtractAppender() {
+		AtomicInteger count = new AtomicInteger(0);
+
+		ExtractAppender p = new ExtractAppender() {
+			@Override
+			protected void append(ILoggingEvent event) {
+				count.incrementAndGet();
+				super.append(event);
+			}
+		};
+
+		addAppender(p);
+
+		logger.info("hello");
+		logger.info("world");
+
+		// "append" should always be called
+		assertEquals(2, count.get());
+
+		// appender with no patterns - everything should match
+		assertEquals(strList("hello", "world"), p.getExtracted());
+
+		// add a pattern and verify match
+		p.setPattern("abc[0-9]");
+		logger.info("hello abc1");
+
+		// this should not match
+		logger.info("hello def2");
+
+		assertEquals(4, count.get());
+		assertEquals(strList("hello", "world", "abc1"), p.getExtracted());
+	}
+
+	@Test
+	public void testExtractAppenderStringArray() {
+		AtomicInteger count = new AtomicInteger(0);
+
+		ExtractAppender p = new ExtractAppender("abc[0-9]", "def[0-9]") {
+			@Override
+			protected void append(ILoggingEvent event) {
+				count.incrementAndGet();
+				super.append(event);
+			}
+		};
+
+		addAppender(p);
+
+		logger.info("hello abc1 world");
+		logger.info("world ghi2 world"); // no match
+		logger.info("world def3 world");
+		logger.info("hello abc4");
+		logger.info("abc5 world");
+		logger.info("hello def6");
+		logger.info("ghi7 world"); // no match
+		logger.info("def8 world");
+
+		// "append" should always be called
+		assertEquals(8, count.get());
+
+		assertEquals(strList("abc1", "def3", "abc4", "abc5", "def6", "def8"), p.getExtracted());
+
+		p.setPattern("ghi[0-9]");
+		logger.info("hello abc9");
+		logger.info("hello ghi9");
+
+		// this should not match
+		logger.info("hello xyz");
+
+		assertEquals(11, count.get());
+		assertEquals(strList("abc1", "def3", "abc4", "abc5", "def6", "def8", "abc9", "ghi9"), p.getExtracted());
+	}
+
+	@Test
+	public void testExtractAppenderQueueStringArray() {
+		// no. of matches allowed in the list
+		int nallowed = 3;
+		
+		AtomicInteger count = new AtomicInteger(0);
+		
+		LinkedList<String> queue = new LinkedList<String>() {
+			private static final long serialVersionUID = 1L;
+
+			@Override
+			public boolean offer(String e) {
+				if(count.incrementAndGet() <= nallowed) {
+					return super.offer(e);
+					
+				} else {
+					return false;
+				}
+			}
+		};
+
+		ExtractAppender p = new ExtractAppender(queue, "abc[0-9]");
+		addAppender(p);
+
+		// these shouldn't match
+		for(int x = 0;  x < 10;  ++x) {
+			logger.info("xyz");
+		}
+		
+		int nmatches = 10;
+
+		LinkedList<String> expected = new LinkedList<>();
+		
+		for(int x = 0;  x < nmatches;  ++x) {
+			String msg = "abc" + x;
+			logger.info(msg + " world");
+			
+			if(x < nallowed) {
+				expected.add(msg);
+			}
+		}
+
+		// "offer" should always be called for a match
+		assertEquals(nmatches, count.get());
+		
+		assertEquals(expected, p.getExtracted());
+	}
+
+	@Test
+	public void testAppendILoggingEvent_NoPatterns() {
+		ExtractAppender p = makeAppender();
+		
+		logger.info("hello");
+		logger.info("world");
+		
+		assertEquals(strList("hello", "world"), p.getExtracted());
+	}
+
+	@Test
+	public void testAppendILoggingEvent_MatchFirstPattern() {
+		ExtractAppender p = makeAppender("abc[0-9]", "def[0-9]");
+		
+		logger.info("hello abc1");
+		logger.info("world xyz2");
+		
+		assertEquals(strList("abc1"), p.getExtracted());
+	}
+
+	@Test
+	public void testAppendILoggingEvent_MatchLastPattern() {
+		ExtractAppender p = makeAppender("abc[0-9]", "def[0-9]");
+		
+		logger.info("hello def1");
+		logger.info("world xyz2");
+		
+		assertEquals(strList("def1"), p.getExtracted());
+	}
+
+	@Test
+	public void testAppendILoggingEvent_Group1() {
+		ExtractAppender p = makeAppender("hello (abc)|(xyz)", "def[0-9]");
+		
+		logger.info("hello abc, world!");
+		logger.info("world abc");
+		
+		assertEquals(strList("abc"), p.getExtracted());
+	}
+
+	@Test
+	public void testAppendILoggingEvent_Group3() {
+		ExtractAppender p = makeAppender("hello (abc)|(pdq)|(xyz)", "def[0-9]");
+		
+		logger.info("say hello xyz, world!");
+		logger.info("world abc");
+		
+		assertEquals(strList("xyz"), p.getExtracted());
+	}
+
+	@Test
+	public void testAppendILoggingEvent_NoGroup() {
+		ExtractAppender p = makeAppender("hello abc");
+		
+		logger.info("say hello abc, world!");
+		logger.info("world abc");
+		
+		assertEquals(strList("hello abc"), p.getExtracted());
+	}
+
+	@Test
+	public void testGetExtracted() {
+		ExtractAppender p = makeAppender("abc[1-9]");
+
+		logger.info("hello abc1 world");
+		logger.info("world ghi2 world"); // no match
+		logger.info("hello abc3");
+
+		List<String> oldlst = p.getExtracted();
+		assertEquals(strList("abc1", "abc3"), oldlst);
+		assertEquals(oldlst, p.getExtracted());
+
+		logger.info("abc9");
+		assertEquals(strList("abc1", "abc3", "abc9"), p.getExtracted());
+	}
+
+	@Test
+	public void testClearExtractions() {
+		ExtractAppender p = makeAppender("abc[1-9]");
+
+		logger.info("hello abc1 world");
+		logger.info("world ghi2 world");
+		logger.info("hello abc3");
+
+		assertEquals(strList("abc1", "abc3"), p.getExtracted());
+
+		p.clearExtractions();
+
+		// list should be empty now
+		assertEquals(strList(), p.getExtracted());
+
+		logger.info("hello abc4 world");
+		logger.info("world ghi5 world");
+		logger.info("hello abc6");
+
+		// list should only contain the new items
+		assertEquals(strList("abc4", "abc6"), p.getExtracted());
+	}
+
+	@Test
+	public void testSetPattern() {
+		ExtractAppender p = makeAppender("abc[1-9]");
+
+		logger.info("hello abc1 world");
+		logger.info("world ghi2 world"); // no match
+		logger.info("hello abc3");
+
+		assertEquals(strList("abc1", "abc3"), p.getExtracted());
+
+		p.setPattern("ghi[0-9]");
+
+		logger.info("world ghi4 world"); // this should match now
+		logger.info("hello abc5"); // this should still match
+		logger.info("hello xyz5"); // no match
+
+		assertEquals(strList("abc1", "abc3", "ghi4", "abc5"), p.getExtracted());
+	}
+
+	/**
+	 * Launches threads doing everything in parallel to ensure nothing crashes.
+	 * 
+	 * @throws Exception
+	 */
+	@Test
+	public void test_MultiThreaded() throws Exception {
+		// when to stop
+		long tend = System.currentTimeMillis() + 250;
+
+		// maximum number of items allowed in the extraction list
+		int maxItems = 10;
+
+		// this will be set if one of the threads generates an error
+		AtomicBoolean err = new AtomicBoolean(false);
+
+		// extracted messages go here - this is a finite-length queue since
+		// we don't know how many messages may actually be logged
+		LinkedList<String> queue = new LinkedList<String>() {
+			private static final long serialVersionUID = 1L;
+
+			@Override
+			public boolean offer(String e) {
+				if (size() < maxItems) {
+					return super.offer(e);
+				} else {
+					return false;
+				}
+			}
+		};
+
+		ExtractAppender app = new ExtractAppender(queue, "abc[1-9]");
+		addAppender(app);
+
+		// create some threads to add another pattern
+		addThread(tend, err, xtxt -> {
+			app.setPattern("def[0-9]");
+		});
+
+		// create some threads to log "abc" messages
+		addThread(tend, err, xtxt -> {
+			logger.info("hello abc" + xtxt + "world!");
+		});
+
+		// create some threads to log "def" messages
+		addThread(tend, err, xtxt -> {
+			logger.info("hello def" + xtxt + "world!");
+		});
+
+		// create some threads to get extractions
+		addThread(tend, err, xtxt -> {
+			app.getExtracted();
+		});
+
+		// create some threads to clear extractions
+		addThread(tend, err, xtxt -> {
+			app.clearExtractions();
+
+			// don't want to clear the list too frequently
+			// so sleep a bit in between
+			try {
+				Thread.sleep(10 + Integer.valueOf(xtxt));
+
+			} catch (InterruptedException e) {
+				Thread.currentThread().interrupt();
+				throw e;
+			}
+		});
+
+		/*
+		 * Finally ready to start.
+		 */
+
+		// start all of the threads
+		for (Thread t : threads) {
+			t.setDaemon(true);
+			t.start();
+		}
+
+		// wait for each thread to stop
+		for (Thread t : threads) {
+			t.join(THREAD_WAIT_MS);
+			assertFalse(t.isAlive());
+		}
+		
+		// ensure none of the threads threw an exception
+		assertFalse(err.get());
+	}
+
+	/**
+	 * Adds multiple threads to perform some function repeatedly until the given
+	 * time is reached.
+	 * 
+	 * @param tend
+	 *            time, in milliseconds, when the test should terminate
+	 * @param haderr
+	 *            this will be set to {@code true} if the function throws an
+	 *            exception other than an InterruptedException
+	 * @param func
+	 *            function to be repeatedly invoked
+	 */
+	private void addThread(long tend, AtomicBoolean haderr, VoidFunction func) {
+		// number of threads of each type to create
+		int neach = 3;
+
+		for (int x = 0; x < neach; ++x) {
+			String xtxt = String.valueOf(x);
+
+			threads.add(new Thread() {
+				@Override
+				public void run() {
+					try {
+						while (System.currentTimeMillis() < tend) {
+							func.apply(xtxt);
+						}
+
+					} catch (InterruptedException ex) {
+						Thread.currentThread().interrupt();
+
+					} catch (Exception ex) {
+						haderr.set(true);
+					}
+				}
+			});
+
+		}
+	}
+
+	/**
+	 * Makes an appender that recognizes the given set of strings.
+	 * 
+	 * @param strings
+	 *            regular expressions to be matched
+	 * @return a new appender
+	 */
+	private ExtractAppender makeAppender(String... strings) {
+		ExtractAppender p = new ExtractAppender(strings);
+
+		addAppender(p);
+
+		return p;
+	}
+
+	/**
+	 * Adds an appender to the logger.
+	 * 
+	 * @param app
+	 *            appender to be added
+	 */
+	private void addAppender(ExtractAppender app) {
+		app.setContext(logger.getLoggerContext());
+		app.start();
+
+		logger.addAppender(app);
+	}
+
+	/**
+	 * Converts an array of strings into a list of strings.
+	 * 
+	 * @param strings
+	 *            array of strings
+	 * @return a list of the strings
+	 */
+	private List<String> strList(String... strings) {
+		return Arrays.asList(strings);
+	}
+
+	@FunctionalInterface
+	public interface VoidFunction {
+		public void apply(String text) throws InterruptedException;
+	}
+}