Add api-resource-locks feature

Added ResourceLockFeatureAPI, to provide an interface for PolicyGuard
to use to access other locking mechanisms.
Move lock API to policy-core.
Changed the interface and added Callback support.  Added a class to
invoke the API implementers.
Changed to set a future instead of expecting the callback to implement
the future interface. Also refactored, creating "lock" sub-package.
Add junit tests.
Increase junit coverage.
IsLocked & isLockedBy should check all arguments.
Make ImplFuture protected instead of public.
Simplify locking - move callback support to an optional feature.
Move Reference class to policy-utils.
Return plain Future instead of LockRequestFuture.

Change-Id: I65154d33833914b4332e02d1ef2512f4c5f09b16
Issue-ID: POLICY-577
Signed-off-by: Jim Hahn <jrh3@att.com>

6 files changed, 1486 insertions, 0 deletions

diff --git a/policy-core/src/test/java/org/onap/policy/drools/core/lock/LockRequestFutureTest.java b/policy-core/src/test/java/org/onap/policy/drools/core/lock/LockRequestFutureTest.java
new file mode 100644
index 00000000..883778eb
--- /dev/null
+++ b/policy-core/src/test/java/org/onap/policy/drools/core/lock/LockRequestFutureTest.java
@@ -0,0 +1,431 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * 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.drools.core.lock;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.onap.policy.drools.core.lock.TestUtils.expectException;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import org.junit.Before;
+import org.junit.Test;
+import org.onap.policy.drools.core.lock.PolicyResourceLockFeatureAPI.Callback;
+
+public class LockRequestFutureTest {
+
+    private static final int WAIT_SEC = 1;
+    private static final String RESOURCE = "my.resource";
+    private static final String OWNER = "my.owner";
+    private static final String EXPECTED_EXCEPTION = "expected exception";
+
+    private Callback callback;
+    private LockRequestFuture fut;
+
+    @Before
+    public void setUp() {
+        callback = mock(Callback.class);
+        fut = new LockRequestFuture(RESOURCE, OWNER, callback);
+    }
+
+    @Test
+    public void testLockRequestFutureStringStringBoolean_False() throws Exception {
+        fut = new LockRequestFuture(RESOURCE, OWNER, false);
+
+        assertTrue(fut.isDone());
+        assertEquals(RESOURCE, fut.getResourceId());
+        assertEquals(OWNER, fut.getOwner());
+
+        assertFalse(fut.isLocked());
+        assertFalse(fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testLockRequestFutureStringStringBoolean_True() throws Exception {
+        fut = new LockRequestFuture(RESOURCE, OWNER, true);
+
+        assertTrue(fut.isDone());
+        assertEquals(RESOURCE, fut.getResourceId());
+        assertEquals(OWNER, fut.getOwner());
+
+        assertTrue(fut.isLocked());
+        assertTrue(fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testLockRequestFutureStringStringBoolean_ArgEx() throws Exception {
+
+        // null resource id
+        IllegalArgumentException ex = expectException(IllegalArgumentException.class,
+                        xxx -> new LockRequestFuture(null, OWNER, true));
+        assertEquals("null resourceId", ex.getMessage());
+
+
+        // null owner
+        ex = expectException(IllegalArgumentException.class, xxx -> new LockRequestFuture(RESOURCE, null, true));
+        assertEquals("null owner", ex.getMessage());
+    }
+
+    @Test
+    public void testLockRequestFutureStringStringCallback() throws Exception {
+        assertFalse(fut.isDone());
+        assertEquals(RESOURCE, fut.getResourceId());
+        assertEquals(OWNER, fut.getOwner());
+
+        fut.setLocked(true);
+        fut.invokeCallback();
+
+        // ensure it invoked the callback
+        verify(callback).set(true);
+    }
+
+    @Test
+    public void testLockRequestFutureStringStringCallback_ArgEx() throws Exception {
+
+        // null resource id
+        IllegalArgumentException ex = expectException(IllegalArgumentException.class,
+                        xxx -> new LockRequestFuture(null, OWNER, callback));
+        assertEquals("null resourceId", ex.getMessage());
+
+
+        // null owner
+        ex = expectException(IllegalArgumentException.class, xxx -> new LockRequestFuture(RESOURCE, null, callback));
+        assertEquals("null owner", ex.getMessage());
+
+
+        // null callback is OK
+        new LockRequestFuture(RESOURCE, OWNER, null);
+    }
+
+    @Test
+    public void testGetResourceId() {
+        assertEquals(RESOURCE, fut.getResourceId());
+    }
+
+    @Test
+    public void testGetOwner() {
+        assertEquals(OWNER, fut.getOwner());
+    }
+
+    @Test
+    public void testCancel() throws Exception {
+        // not cancelled yet
+        assertFalse(fut.isDone());
+
+        // cancel it
+        assertTrue(fut.cancel(false));
+        assertTrue(fut.isDone());
+
+        // should not block now
+        expectException(CancellationException.class, xxx -> fut.get(0, TimeUnit.SECONDS));
+
+    }
+
+    @Test
+    public void testCancel_AlreadyCancelled() throws Exception {
+
+        fut.cancel(true);
+
+        assertFalse(fut.cancel(true));
+        assertTrue(fut.isDone());
+
+        expectException(CancellationException.class, xxx -> fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testCancel_AlreadyAcquired() throws Exception {
+
+        fut.setLocked(true);
+
+        assertFalse(fut.cancel(true));
+        assertTrue(fut.isDone());
+        assertTrue(fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testCancel_AlreadyDenied() throws Exception {
+
+        fut.setLocked(false);
+
+        assertFalse(fut.cancel(true));
+        assertTrue(fut.isDone());
+        assertFalse(fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testSetLocked_True() throws Exception {
+        assertTrue(fut.setLocked(true));
+
+        assertTrue(fut.isDone());
+        assertTrue(fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testSetLocked_False() throws Exception {
+        assertTrue(fut.setLocked(false));
+
+        assertTrue(fut.isDone());
+        assertFalse(fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testSetLocked_AlreadyCancelled() {
+
+        fut.cancel(true);
+
+        assertFalse(fut.setLocked(true));
+        assertFalse(fut.setLocked(false));
+
+        assertTrue(fut.isDone());
+        expectException(CancellationException.class, xxx -> fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testSetLocked_AlreadyAcquired() throws Exception {
+        fut.setLocked(true);
+
+        assertTrue(fut.isDone());
+        assertTrue(fut.get(0, TimeUnit.SECONDS));
+
+        assertFalse(fut.cancel(true));
+        assertFalse(fut.setLocked(true));
+        assertFalse(fut.setLocked(false));
+    }
+
+    @Test
+    public void testSetLocked_AlreadyDenied() throws Exception {
+        fut.setLocked(false);
+
+        assertTrue(fut.isDone());
+        assertFalse(fut.get(0, TimeUnit.SECONDS));
+
+        assertFalse(fut.cancel(true));
+        assertFalse(fut.setLocked(true));
+        assertFalse(fut.setLocked(false));
+    }
+
+    @Test
+    public void testIsCancelled() {
+        assertFalse(fut.isCancelled());
+
+        fut.cancel(false);
+        assertTrue(fut.isCancelled());
+    }
+
+    @Test
+    public void testIsCancelled_Acquired() {
+        fut.setLocked(true);
+        assertFalse(fut.isCancelled());
+    }
+
+    @Test
+    public void testIsCancelled_Denied() {
+        fut.setLocked(false);
+        assertFalse(fut.isCancelled());
+    }
+
+    @Test
+    public void testIsDone_Cancelled() {
+        fut.cancel(false);
+        assertTrue(fut.isDone());
+    }
+
+    @Test
+    public void testIsDone_Acquired() {
+        fut.setLocked(true);
+        assertTrue(fut.isDone());
+    }
+
+    @Test
+    public void testIsDone_Denied() {
+        fut.setLocked(false);
+        assertTrue(fut.isDone());
+    }
+
+    @Test
+    public void testIsDone_Waiting() {
+        assertFalse(fut.isDone());
+    }
+
+    @Test
+    public void testIsLocked_Cancelled() {
+        fut.cancel(false);
+        assertFalse(fut.isLocked());
+    }
+
+    @Test
+    public void testIsLocked_Acquired() {
+        fut.setLocked(true);
+        assertTrue(fut.isLocked());
+    }
+
+    @Test
+    public void testIsLocked_Denied() {
+        fut.setLocked(false);
+        assertFalse(fut.isLocked());
+    }
+
+    @Test
+    public void testIsLocked_Waiting() {
+        assertFalse(fut.isLocked());
+    }
+
+    @Test
+    public void testGet_Cancelled() throws Exception {
+        new Thread() {
+            @Override
+            public void run() {
+                fut.cancel(false);
+            }
+        }.start();
+
+        expectException(CancellationException.class, xxx -> fut.get());
+    }
+
+    @Test
+    public void testGet_Acquired() throws Exception {
+        new Thread() {
+            @Override
+            public void run() {
+                fut.setLocked(true);
+            }
+        }.start();
+
+        assertTrue(fut.get());
+    }
+
+    @Test
+    public void testGet_Denied() throws Exception {
+        new Thread() {
+            @Override
+            public void run() {
+                fut.setLocked(false);
+            }
+        }.start();
+
+        assertFalse(fut.get());
+    }
+
+    @Test
+    public void testGetLongTimeUnit() throws Exception {
+        expectException(TimeoutException.class, xxx -> fut.get(0, TimeUnit.SECONDS));
+
+        fut.setLocked(true);
+        assertTrue(fut.get(0, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testGetLongTimeUnit_Timeout() throws Exception {
+        expectException(TimeoutException.class, xxx -> fut.get(0, TimeUnit.SECONDS));
+        expectException(TimeoutException.class, xxx -> fut.get(2, TimeUnit.MILLISECONDS));
+    }
+
+    @Test
+    public void testGetLongTimeUnit_Cancelled() throws Exception {
+        new Thread() {
+            @Override
+            public void run() {
+                fut.cancel(false);
+            }
+        }.start();
+
+        expectException(CancellationException.class, xxx -> fut.get(WAIT_SEC, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testGetLongTimeUnit_Acquired() throws Exception {
+        new Thread() {
+            @Override
+            public void run() {
+                fut.setLocked(true);
+            }
+        }.start();
+
+        assertTrue(fut.get(WAIT_SEC, TimeUnit.SECONDS));
+    }
+
+    @Test
+    public void testGetLongTimeUnit_Denied() throws Exception {
+        new Thread() {
+            @Override
+            public void run() {
+                fut.setLocked(false);
+            }
+        }.start();
+
+        assertFalse(fut.get(WAIT_SEC, TimeUnit.SECONDS));
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testInvokeCallback() {
+        fut.setLocked(true);
+        fut.invokeCallback();
+
+        // re-invoke - should throw an exception
+        fut.invokeCallback();
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testInvokeCallback_Cancelled() {
+        fut.cancel(false);
+
+        // invoke after cancel - should throw an exception
+        fut.invokeCallback();
+    }
+
+    @Test
+    public void testInvokeCallback_Acquired() {
+        fut.setLocked(true);
+        fut.invokeCallback();
+
+        verify(callback).set(true);
+        verify(callback, never()).set(false);
+    }
+
+    @Test
+    public void testInvokeCallback_Denied() {
+        fut.setLocked(false);
+        fut.invokeCallback();
+
+        verify(callback).set(false);
+        verify(callback, never()).set(true);
+    }
+
+    @Test
+    public void testInvokeCallback_Ex() {
+        doThrow(new RuntimeException(EXPECTED_EXCEPTION)).when(callback).set(anyBoolean());
+
+        fut.setLocked(false);
+        fut.invokeCallback();
+    }
+
+    @Test
+    public void testMakeNullArgException() {
+        IllegalArgumentException ex = LockRequestFuture.makeNullArgException(EXPECTED_EXCEPTION);
+        assertEquals(EXPECTED_EXCEPTION, ex.getMessage());
+    }
+}
diff --git a/policy-core/src/test/java/org/onap/policy/drools/core/lock/LockTest.java b/policy-core/src/test/java/org/onap/policy/drools/core/lock/LockTest.java
new file mode 100644
index 00000000..bd11dcf9
--- /dev/null
+++ b/policy-core/src/test/java/org/onap/policy/drools/core/lock/LockTest.java
@@ -0,0 +1,131 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * 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.drools.core.lock;
+
+import static org.junit.Assert.*;
+import org.junit.Before;
+import org.junit.Test;
+import org.onap.policy.drools.core.lock.Lock.RemoveResult;
+import org.onap.policy.drools.utils.Pair;
+
+public class LockTest {
+    
+    private static final String OWNER = "my.owner";
+    private static final String OWNER2 = "another.owner";
+    private static final String OWNER3 = "third.owner";
+    
+    private static final Integer ITEM2 = 10;
+    private static final Integer ITEM3 = 20;
+    
+    private Lock<Integer> lock;
+    private Pair<String, Integer> newOwner;
+    
+    @Before
+    public void setUp() {
+        lock = new Lock<>(OWNER);
+        newOwner = new Pair<>(null, null);
+    }
+    
+
+    @Test
+    public void testLock() {
+        assertEquals(OWNER, lock.getOwner());
+    }
+
+    @Test
+    public void testGetOwner() {
+        assertEquals(OWNER, lock.getOwner());
+    }
+
+    @Test
+    public void testAdd() {
+        assertTrue(lock.add(OWNER2, ITEM2));
+        assertTrue(lock.add(OWNER3, ITEM3));
+        
+        // attempt to re-add owner2 with the same item - should fail
+        assertFalse(lock.add(OWNER2, ITEM2));
+        
+        // attempt to re-add owner2 with a different item - should fail
+        assertFalse(lock.add(OWNER2, ITEM3));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testAdd_ArgEx() {
+        lock.add(OWNER2, null);
+    }
+
+    @Test
+    public void testAdd_AlreadyOwner() {
+        assertFalse(lock.add(OWNER, ITEM2));
+    }
+
+    @Test
+    public void testAdd_AlreadyInQueue() {
+        lock.add(OWNER2, ITEM2);
+
+        assertFalse(lock.add(OWNER2, ITEM2));
+    }
+
+    @Test
+    public void testRemoveRequester_Owner_QueueEmpty() {
+        assertEquals(RemoveResult.UNLOCKED, lock.removeRequester(OWNER, newOwner));
+    }
+
+    @Test
+    public void testRemoveRequester_Owner_QueueHasOneItem() {
+        lock.add(OWNER2, ITEM2);
+        
+        assertEquals(RemoveResult.RELOCKED, lock.removeRequester(OWNER, newOwner));
+        assertEquals(OWNER2, newOwner.first());
+        assertEquals(ITEM2, newOwner.second());
+
+        assertEquals(RemoveResult.UNLOCKED, lock.removeRequester(OWNER2, newOwner));
+    }
+
+    @Test
+    public void testRemoveRequester_Owner_QueueHasMultipleItems() {
+        lock.add(OWNER2, ITEM2);
+        lock.add(OWNER3, ITEM3);
+        
+        assertEquals(RemoveResult.RELOCKED, lock.removeRequester(OWNER, newOwner));
+        assertEquals(OWNER2, newOwner.first());
+        assertEquals(ITEM2, newOwner.second());
+        
+        assertEquals(RemoveResult.RELOCKED, lock.removeRequester(OWNER2, newOwner));
+        assertEquals(OWNER3, newOwner.first());
+        assertEquals(ITEM3, newOwner.second());
+
+        assertEquals(RemoveResult.UNLOCKED, lock.removeRequester(OWNER3, newOwner));
+    }
+
+    @Test
+    public void testRemoveRequester_InQueue() {
+        lock.add(OWNER2, ITEM2);
+        
+        assertEquals(RemoveResult.REMOVED, lock.removeRequester(OWNER2, newOwner));
+    }
+
+    @Test
+    public void testRemoveRequester_NeitherOwnerNorInQueue() {
+        assertEquals(RemoveResult.NOT_FOUND, lock.removeRequester(OWNER2, newOwner));
+    }
+
+}
diff --git a/policy-core/src/test/java/org/onap/policy/drools/core/lock/PolicyResourceLockFeatureAPITest.java b/policy-core/src/test/java/org/onap/policy/drools/core/lock/PolicyResourceLockFeatureAPITest.java
new file mode 100644
index 00000000..5a826bb7
--- /dev/null
+++ b/policy-core/src/test/java/org/onap/policy/drools/core/lock/PolicyResourceLockFeatureAPITest.java
@@ -0,0 +1,76 @@
+/*
+ * ============LICENSE_START=======================================================
+ * api-resource-locks
+ * ================================================================================
+ * 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.drools.core.lock;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import org.junit.Before;
+import org.junit.Test;
+
+public class PolicyResourceLockFeatureAPITest {
+
+    private static final String RESOURCE_ID = "the resource";
+    private static final String OWNER = "the owner";
+
+    private PolicyResourceLockFeatureAPI api;
+
+    @Before
+    public void setUp() {
+        api = new PolicyResourceLockFeatureAPI() {
+            @Override
+            public int getSequenceNumber() {
+                return 0;
+            }
+        };
+    }
+
+    @Test
+    public void testBeforeLock() {
+        assertNull(api.beforeLock(RESOURCE_ID, OWNER, null));
+    }
+
+    @Test
+    public void testAfterLock() {
+        assertFalse(api.afterLock(RESOURCE_ID, OWNER, true));
+        assertFalse(api.afterLock(RESOURCE_ID, OWNER, false));
+    }
+
+    @Test
+    public void testBeforeUnlock() {
+        assertNull(api.beforeUnlock(RESOURCE_ID, OWNER));
+    }
+
+    @Test
+    public void testAfterUnlock() {
+        assertFalse(api.afterUnlock(RESOURCE_ID, OWNER, true));
+        assertFalse(api.afterUnlock(RESOURCE_ID, OWNER, false));
+    }
+
+    @Test
+    public void testBeforeIsLocked() {
+        assertNull(api.beforeIsLocked(RESOURCE_ID));
+    }
+
+    @Test
+    public void testBeforeIsLockedBy() {
+        assertNull(api.beforeIsLockedBy(RESOURCE_ID, OWNER));
+    }
+}
diff --git a/policy-core/src/test/java/org/onap/policy/drools/core/lock/PolicyResourceLockManagerTest.java b/policy-core/src/test/java/org/onap/policy/drools/core/lock/PolicyResourceLockManagerTest.java
new file mode 100644
index 00000000..2f8b5f83
--- /dev/null
+++ b/policy-core/src/test/java/org/onap/policy/drools/core/lock/PolicyResourceLockManagerTest.java
@@ -0,0 +1,509 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * 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.drools.core.lock;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+import static org.onap.policy.drools.core.lock.TestUtils.expectException;
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.concurrent.Future;
+import org.junit.AfterClass;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.onap.policy.drools.core.lock.PolicyResourceLockFeatureAPI.Callback;
+import org.onap.policy.drools.core.lock.PolicyResourceLockManager.Factory;
+
+public class PolicyResourceLockManagerTest {
+
+    private static final String NULL_RESOURCE_ID = "null resourceId";
+    private static final String NULL_OWNER = "null owner";
+
+    private static final String RESOURCE_A = "resource.a";
+    private static final String RESOURCE_B = "resource.b";
+    private static final String RESOURCE_C = "resource.c";
+
+    private static final String OWNER1 = "owner.one";
+    private static final String OWNER2 = "owner.two";
+    private static final String OWNER3 = "owner.three";
+
+    /**
+     * Saved at the start of the tests and restored once all tests complete.
+     */
+    private static Factory saveFactory;
+
+    private Callback callback1;
+    private PolicyResourceLockFeatureAPI impl1;
+    private PolicyResourceLockFeatureAPI impl2;
+    private List<PolicyResourceLockFeatureAPI> implList;
+
+    private Future<Boolean> fut;
+
+    private PolicyResourceLockManager mgr;
+
+    @BeforeClass
+    public static void setUpBeforeClass() {
+        saveFactory = PolicyResourceLockManager.getFactory();
+    }
+
+    @AfterClass
+    public static void tearDownAfterClass() {
+        PolicyResourceLockManager.setFactory(saveFactory);
+    }
+
+    @Before
+    public void setUp() {
+        callback1 = mock(Callback.class);
+        impl1 = mock(PolicyResourceLockFeatureAPI.class);
+        impl2 = mock(PolicyResourceLockFeatureAPI.class);
+
+        initImplementer(impl1);
+        initImplementer(impl2);
+
+        // list of feature API implementers
+        implList = new LinkedList<>(Arrays.asList(impl1, impl2));
+
+        PolicyResourceLockManager.setFactory(new Factory() {
+
+            @Override
+            public List<PolicyResourceLockFeatureAPI> getImplementers() {
+                return implList;
+            }
+        });
+
+        mgr = new PolicyResourceLockManager();
+    }
+
+    /**
+     * Initializes an implementer so it always returns {@code null}.
+     * 
+     * @param impl
+     */
+    private void initImplementer(PolicyResourceLockFeatureAPI impl) {
+        when(impl.beforeLock(anyString(), anyString(), any(Callback.class))).thenReturn(null);
+        when(impl.beforeUnlock(anyString(), anyString())).thenReturn(null);
+        when(impl.beforeIsLocked(anyString())).thenReturn(null);
+        when(impl.beforeIsLockedBy(anyString(), anyString())).thenReturn(null);
+    }
+
+    @Test
+    public void testLock() throws Exception {
+        fut = mgr.lock(RESOURCE_A, OWNER1, callback1);
+
+        assertTrue(fut.isDone());
+        assertTrue(fut.get());
+
+        verify(impl1).beforeLock(RESOURCE_A, OWNER1, callback1);
+        verify(impl2).beforeLock(RESOURCE_A, OWNER1, callback1);
+        verify(impl1).afterLock(RESOURCE_A, OWNER1, true);
+        verify(impl2).afterLock(RESOURCE_A, OWNER1, true);
+
+        assertTrue(mgr.isLocked(RESOURCE_A));
+        assertTrue(mgr.isLockedBy(RESOURCE_A, OWNER1));
+        assertFalse(mgr.isLocked(RESOURCE_B));
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER2));
+
+        // null callback - not locked yet
+        fut = mgr.lock(RESOURCE_C, OWNER3, null);
+        assertTrue(fut.isDone());
+        assertTrue(fut.get());
+
+        // null callback - already locked
+        fut = mgr.lock(RESOURCE_A, OWNER3, null);
+        assertTrue(fut.isDone());
+        assertFalse(fut.get());
+    }
+
+    @Test
+    public void testLock_ArgEx() {
+        IllegalArgumentException ex =
+                        expectException(IllegalArgumentException.class, xxx -> mgr.lock(null, OWNER1, callback1));
+        assertEquals(NULL_RESOURCE_ID, ex.getMessage());
+
+        ex = expectException(IllegalArgumentException.class, xxx -> mgr.lock(RESOURCE_A, null, callback1));
+        assertEquals(NULL_OWNER, ex.getMessage());
+
+        // this should not throw an exception
+        mgr.lock(RESOURCE_A, OWNER1, null);
+    }
+
+    @Test
+    public void testLock_BeforeIntercepted() {
+        fut = mock(LockRequestFuture.class);
+
+        // NOT async
+        when(fut.isDone()).thenReturn(true);
+
+        // have impl1 intercept
+        when(impl1.beforeLock(RESOURCE_A, OWNER1, callback1)).thenReturn(fut);
+
+        assertEquals(fut, mgr.lock(RESOURCE_A, OWNER1, callback1));
+
+        verify(impl1).beforeLock(RESOURCE_A, OWNER1, callback1);
+        verify(impl2, never()).beforeLock(anyString(), anyString(), any(Callback.class));
+
+        verify(impl1, never()).afterLock(anyString(), anyString(), anyBoolean());
+        verify(impl2, never()).afterLock(anyString(), anyString(), anyBoolean());
+    }
+
+    @Test
+    public void testLock_Acquired_AfterIntercepted() throws Exception {
+
+        // impl1 intercepts during afterLock()
+        when(impl1.afterLock(RESOURCE_A, OWNER1, true)).thenReturn(true);
+
+        fut = mgr.lock(RESOURCE_A, OWNER1, callback1);
+
+        assertTrue(fut.isDone());
+        assertTrue(fut.get());
+
+        // impl1 sees it, but impl2 does not
+        verify(impl1).afterLock(RESOURCE_A, OWNER1, true);
+        verify(impl2, never()).afterLock(anyString(), anyString(), anyBoolean());
+    }
+
+    @Test
+    public void testLock_Acquired() throws Exception {
+        fut = mgr.lock(RESOURCE_A, OWNER1, callback1);
+
+        assertTrue(fut.isDone());
+        assertTrue(fut.get());
+
+        verify(impl1).afterLock(RESOURCE_A, OWNER1, true);
+        verify(impl2).afterLock(RESOURCE_A, OWNER1, true);
+    }
+
+    @Test
+    public void testLock_Denied_AfterIntercepted() throws Exception {
+
+        mgr.lock(RESOURCE_A, OWNER1, callback1);
+
+        // impl1 intercepts during afterLock()
+        when(impl1.afterLock(RESOURCE_A, OWNER2, false)).thenReturn(true);
+
+        // owner2 tries to lock
+        fut = mgr.lock(RESOURCE_A, OWNER2, null);
+
+        assertTrue(fut.isDone());
+        assertFalse(fut.get());
+
+        // impl1 sees it, but impl2 does not
+        verify(impl1).afterLock(RESOURCE_A, OWNER2, false);
+        verify(impl2, never()).afterLock(RESOURCE_A, OWNER2, false);
+    }
+
+    @Test
+    public void testLock_Denied() {
+
+        mgr.lock(RESOURCE_A, OWNER1, callback1);
+
+        // owner2 tries to lock
+        fut = mgr.lock(RESOURCE_A, OWNER2, null);
+
+        verify(impl1).afterLock(RESOURCE_A, OWNER2, false);
+        verify(impl2).afterLock(RESOURCE_A, OWNER2, false);
+    }
+
+    @Test
+    public void testUnlock() throws Exception {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+        mgr.lock(RESOURCE_B, OWNER1, null);
+
+        assertTrue(mgr.unlock(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeUnlock(RESOURCE_A, OWNER1);
+        verify(impl2).beforeUnlock(RESOURCE_A, OWNER1);
+
+        verify(impl1).afterUnlock(RESOURCE_A, OWNER1, true);
+        verify(impl2).afterUnlock(RESOURCE_A, OWNER1, true);
+    }
+
+    @Test
+    public void testUnlock_ArgEx() {
+        IllegalArgumentException ex = expectException(IllegalArgumentException.class, xxx -> mgr.unlock(null, OWNER1));
+        assertEquals(NULL_RESOURCE_ID, ex.getMessage());
+
+        ex = expectException(IllegalArgumentException.class, xxx -> mgr.unlock(RESOURCE_A, null));
+        assertEquals(NULL_OWNER, ex.getMessage());
+    }
+
+    @Test
+    public void testUnlock_BeforeInterceptedTrue() {
+
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        // have impl1 intercept
+        when(impl1.beforeUnlock(RESOURCE_A, OWNER1)).thenReturn(true);
+
+        assertTrue(mgr.unlock(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeUnlock(RESOURCE_A, OWNER1);
+        verify(impl2, never()).beforeUnlock(anyString(), anyString());
+
+        verify(impl1, never()).afterUnlock(anyString(), anyString(), anyBoolean());
+        verify(impl2, never()).afterUnlock(anyString(), anyString(), anyBoolean());
+    }
+
+    @Test
+    public void testUnlock_BeforeInterceptedFalse() {
+
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        // have impl1 intercept
+        when(impl1.beforeUnlock(RESOURCE_A, OWNER1)).thenReturn(false);
+
+        assertFalse(mgr.unlock(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeUnlock(RESOURCE_A, OWNER1);
+        verify(impl2, never()).beforeUnlock(anyString(), anyString());
+
+        verify(impl1, never()).afterUnlock(anyString(), anyString(), anyBoolean());
+        verify(impl2, never()).afterUnlock(anyString(), anyString(), anyBoolean());
+    }
+
+    @Test
+    public void testUnlock_Unlocked() {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        assertTrue(mgr.unlock(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeUnlock(RESOURCE_A, OWNER1);
+        verify(impl2).beforeUnlock(RESOURCE_A, OWNER1);
+
+        verify(impl1).afterUnlock(RESOURCE_A, OWNER1, true);
+        verify(impl2).afterUnlock(RESOURCE_A, OWNER1, true);
+    }
+
+    @Test
+    public void testUnlock_Unlocked_AfterIntercepted() {
+        // have impl1 intercept
+        when(impl1.afterUnlock(RESOURCE_A, OWNER1, true)).thenReturn(true);
+
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        assertTrue(mgr.unlock(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeUnlock(RESOURCE_A, OWNER1);
+        verify(impl2).beforeUnlock(RESOURCE_A, OWNER1);
+
+        verify(impl1).afterUnlock(RESOURCE_A, OWNER1, true);
+        verify(impl2, never()).afterUnlock(RESOURCE_A, OWNER1, true);
+    }
+
+    @Test
+    public void testUnlock_NotUnlocked() {
+        assertFalse(mgr.unlock(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeUnlock(RESOURCE_A, OWNER1);
+        verify(impl2).beforeUnlock(RESOURCE_A, OWNER1);
+
+        verify(impl1).afterUnlock(RESOURCE_A, OWNER1, false);
+        verify(impl2).afterUnlock(RESOURCE_A, OWNER1, false);
+    }
+
+    @Test
+    public void testUnlock_NotUnlocked_AfterIntercepted() {
+        // have impl1 intercept
+        when(impl1.afterUnlock(RESOURCE_A, OWNER1, false)).thenReturn(true);
+
+        assertFalse(mgr.unlock(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeUnlock(RESOURCE_A, OWNER1);
+        verify(impl2).beforeUnlock(RESOURCE_A, OWNER1);
+
+        verify(impl1).afterUnlock(RESOURCE_A, OWNER1, false);
+        verify(impl2, never()).afterUnlock(RESOURCE_A, OWNER1, false);
+    }
+
+    @Test
+    public void testIsLocked_True() {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        assertTrue(mgr.isLocked(RESOURCE_A));
+
+        verify(impl1).beforeIsLocked(RESOURCE_A);
+        verify(impl2).beforeIsLocked(RESOURCE_A);
+    }
+
+    @Test
+    public void testIsLocked_False() {
+        assertFalse(mgr.isLocked(RESOURCE_A));
+
+        verify(impl1).beforeIsLocked(RESOURCE_A);
+        verify(impl2).beforeIsLocked(RESOURCE_A);
+    }
+
+    @Test
+    public void testIsLocked_ArgEx() {
+        IllegalArgumentException ex = expectException(IllegalArgumentException.class, xxx -> mgr.isLocked(null));
+        assertEquals(NULL_RESOURCE_ID, ex.getMessage());
+    }
+
+    @Test
+    public void testIsLocked_BeforeIntercepted_True() {
+
+        // have impl1 intercept
+        when(impl1.beforeIsLocked(RESOURCE_A)).thenReturn(true);
+
+        assertTrue(mgr.isLocked(RESOURCE_A));
+
+        verify(impl1).beforeIsLocked(RESOURCE_A);
+        verify(impl2, never()).beforeIsLocked(RESOURCE_A);
+    }
+
+    @Test
+    public void testIsLocked_BeforeIntercepted_False() {
+
+        // lock it so we can verify that impl1 overrides the superclass isLocker()
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        // have impl1 intercept
+        when(impl1.beforeIsLocked(RESOURCE_A)).thenReturn(false);
+
+        assertFalse(mgr.isLocked(RESOURCE_A));
+
+        verify(impl1).beforeIsLocked(RESOURCE_A);
+        verify(impl2, never()).beforeIsLocked(RESOURCE_A);
+    }
+
+    @Test
+    public void testIsLockedBy_True() {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        assertTrue(mgr.isLockedBy(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeIsLockedBy(RESOURCE_A, OWNER1);
+        verify(impl2).beforeIsLockedBy(RESOURCE_A, OWNER1);
+    }
+
+    @Test
+    public void testIsLockedBy_False() {
+        // different owner
+        mgr.lock(RESOURCE_A, OWNER2, null);
+
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeIsLockedBy(RESOURCE_A, OWNER1);
+        verify(impl2).beforeIsLockedBy(RESOURCE_A, OWNER1);
+    }
+
+    @Test
+    public void testIsLockedBy_ArgEx() {
+        IllegalArgumentException ex =
+                        expectException(IllegalArgumentException.class, xxx -> mgr.isLockedBy(null, OWNER1));
+        assertEquals(NULL_RESOURCE_ID, ex.getMessage());
+
+        ex = expectException(IllegalArgumentException.class, xxx -> mgr.isLockedBy(RESOURCE_A, null));
+        assertEquals(NULL_OWNER, ex.getMessage());
+    }
+
+    @Test
+    public void testIsLockedBy_BeforeIntercepted_True() {
+
+        // have impl1 intercept
+        when(impl1.beforeIsLockedBy(RESOURCE_A, OWNER1)).thenReturn(true);
+
+        assertTrue(mgr.isLockedBy(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeIsLockedBy(RESOURCE_A, OWNER1);
+        verify(impl2, never()).beforeIsLockedBy(RESOURCE_A, OWNER1);
+    }
+
+    @Test
+    public void testIsLockedBy_BeforeIntercepted_False() {
+
+        // lock it so we can verify that impl1 overrides the superclass isLocker()
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        // have impl1 intercept
+        when(impl1.beforeIsLockedBy(RESOURCE_A, OWNER1)).thenReturn(false);
+
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER1));
+
+        verify(impl1).beforeIsLockedBy(RESOURCE_A, OWNER1);
+        verify(impl2, never()).beforeIsLockedBy(RESOURCE_A, OWNER1);
+    }
+
+    @Test
+    public void testGetInstance() {
+        PolicyResourceLockManager inst = PolicyResourceLockManager.getInstance();
+        assertNotNull(inst);
+
+        // should return the same instance each time
+        assertEquals(inst, PolicyResourceLockManager.getInstance());
+        assertEquals(inst, PolicyResourceLockManager.getInstance());
+    }
+
+    @Test
+    public void testDoIntercept_Empty() {
+        // clear the implementer list
+        implList.clear();
+
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        assertTrue(mgr.isLocked(RESOURCE_A));
+        assertFalse(mgr.isLocked(RESOURCE_B));
+
+        verify(impl1, never()).beforeIsLocked(anyString());
+    }
+
+    @Test
+    public void testDoIntercept_Impl1() {
+        when(impl1.beforeIsLocked(RESOURCE_A)).thenReturn(true);
+
+        assertTrue(mgr.isLocked(RESOURCE_A));
+
+        verify(impl1).beforeIsLocked(RESOURCE_A);
+        verify(impl2, never()).beforeIsLocked(anyString());
+    }
+
+    @Test
+    public void testDoIntercept_Impl2() {
+        when(impl2.beforeIsLocked(RESOURCE_A)).thenReturn(true);
+
+        assertTrue(mgr.isLocked(RESOURCE_A));
+
+        verify(impl1).beforeIsLocked(RESOURCE_A);
+        verify(impl2).beforeIsLocked(RESOURCE_A);
+    }
+
+    @Test
+    public void testDoIntercept_Ex() {
+        doThrow(new RuntimeException("expected exception")).when(impl1).beforeIsLocked(RESOURCE_A);
+
+        assertFalse(mgr.isLocked(RESOURCE_A));
+
+        verify(impl1).beforeIsLocked(RESOURCE_A);
+        verify(impl2).beforeIsLocked(RESOURCE_A);
+    }
+}
diff --git a/policy-core/src/test/java/org/onap/policy/drools/core/lock/SimpleLockManagerTest.java b/policy-core/src/test/java/org/onap/policy/drools/core/lock/SimpleLockManagerTest.java
new file mode 100644
index 00000000..6abc5bf9
--- /dev/null
+++ b/policy-core/src/test/java/org/onap/policy/drools/core/lock/SimpleLockManagerTest.java
@@ -0,0 +1,280 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * 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.drools.core.lock;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.onap.policy.drools.core.lock.TestUtils.expectException;
+import java.util.LinkedList;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import org.junit.Before;
+import org.junit.Test;
+
+public class SimpleLockManagerTest {
+
+    private static final String NULL_RESOURCE_ID = "null resourceId";
+    private static final String NULL_OWNER = "null owner";
+
+    private static final String RESOURCE_A = "resource.a";
+    private static final String RESOURCE_B = "resource.b";
+    private static final String RESOURCE_C = "resource.c";
+
+    private static final String OWNER1 = "owner.one";
+    private static final String OWNER2 = "owner.two";
+    private static final String OWNER3 = "owner.three";
+
+    private Future<Boolean> fut;
+    private SimpleLockManager mgr;
+
+    @Before
+    public void setUp() {
+        mgr = new SimpleLockManager();
+    }
+
+    @Test
+    public void testLock() throws Exception {
+        fut = mgr.lock(RESOURCE_A, OWNER1, null);
+
+        assertTrue(fut.isDone());
+        assertTrue(fut.get());
+
+        assertTrue(mgr.isLocked(RESOURCE_A));
+        assertTrue(mgr.isLockedBy(RESOURCE_A, OWNER1));
+        assertFalse(mgr.isLocked(RESOURCE_B));
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER2));
+
+        // null callback - not locked yet
+        fut = mgr.lock(RESOURCE_C, OWNER3, null);
+        assertTrue(fut.isDone());
+        assertTrue(fut.get());
+
+        // null callback - already locked
+        fut = mgr.lock(RESOURCE_A, OWNER3, null);
+        assertTrue(fut.isDone());
+        assertFalse(fut.get());
+    }
+
+    @Test
+    public void testLock_AlreadyLocked() throws Exception {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        fut = mgr.lock(RESOURCE_A, OWNER2, null);
+        assertTrue(fut.isDone());
+        assertFalse(fut.get());
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testLock_SameOwner() throws Exception {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        // should throw an exception
+        mgr.lock(RESOURCE_A, OWNER1, null);
+    }
+
+    @Test
+    public void testLock_ArgEx() {
+        IllegalArgumentException ex =
+                        expectException(IllegalArgumentException.class, xxx -> mgr.lock(null, OWNER1, null));
+        assertEquals(NULL_RESOURCE_ID, ex.getMessage());
+
+        ex = expectException(IllegalArgumentException.class, xxx -> mgr.lock(RESOURCE_A, null, null));
+        assertEquals(NULL_OWNER, ex.getMessage());
+
+        // this should not throw an exception
+        mgr.lock(RESOURCE_A, OWNER1, null);
+    }
+
+    @Test
+    public void testUnlock() throws Exception {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        // unlock it
+        assertTrue(mgr.unlock(RESOURCE_A, OWNER1));
+    }
+
+    @Test
+    public void testUnlock_ArgEx() {
+        IllegalArgumentException ex = expectException(IllegalArgumentException.class, xxx -> mgr.unlock(null, OWNER1));
+        assertEquals(NULL_RESOURCE_ID, ex.getMessage());
+
+        ex = expectException(IllegalArgumentException.class, xxx -> mgr.unlock(RESOURCE_A, null));
+        assertEquals(NULL_OWNER, ex.getMessage());
+    }
+
+    @Test
+    public void testUnlock_NotLocked() {
+        assertFalse(mgr.unlock(RESOURCE_A, OWNER1));
+    }
+
+    @Test
+    public void testIsLocked() {
+        assertFalse(mgr.isLocked(RESOURCE_A));
+
+        mgr.lock(RESOURCE_A, OWNER1, null);
+        mgr.lock(RESOURCE_B, OWNER1, null);
+
+        assertTrue(mgr.isLocked(RESOURCE_A));
+        assertTrue(mgr.isLocked(RESOURCE_B));
+        assertFalse(mgr.isLocked(RESOURCE_C));
+
+        // unlock from first resource
+        mgr.unlock(RESOURCE_A, OWNER1);
+        assertFalse(mgr.isLocked(RESOURCE_A));
+        assertTrue(mgr.isLocked(RESOURCE_B));
+        assertFalse(mgr.isLocked(RESOURCE_C));
+
+        // unlock from second resource
+        mgr.unlock(RESOURCE_B, OWNER1);
+        assertFalse(mgr.isLocked(RESOURCE_A));
+        assertFalse(mgr.isLocked(RESOURCE_B));
+        assertFalse(mgr.isLocked(RESOURCE_C));
+    }
+
+    @Test
+    public void testIsLocked_ArgEx() {
+        IllegalArgumentException ex = expectException(IllegalArgumentException.class, xxx -> mgr.isLocked(null));
+        assertEquals(NULL_RESOURCE_ID, ex.getMessage());
+    }
+
+    @Test
+    public void testIsLockedBy() {
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER1));
+
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        assertFalse(mgr.isLockedBy(RESOURCE_B, OWNER1));
+
+        assertTrue(mgr.isLockedBy(RESOURCE_A, OWNER1));
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER2));
+
+        // unlock from the resource
+        mgr.unlock(RESOURCE_A, OWNER1);
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER1));
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER2));
+        assertFalse(mgr.isLockedBy(RESOURCE_B, OWNER1));
+    }
+
+    @Test
+    public void testIsLockedBy_ArgEx() {
+        IllegalArgumentException ex =
+                        expectException(IllegalArgumentException.class, xxx -> mgr.isLockedBy(null, OWNER1));
+        assertEquals(NULL_RESOURCE_ID, ex.getMessage());
+
+        ex = expectException(IllegalArgumentException.class, xxx -> mgr.isLockedBy(RESOURCE_A, null));
+        assertEquals(NULL_OWNER, ex.getMessage());
+    }
+
+    @Test
+    public void testIsLockedBy_NotLocked() {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        // different resource, thus no lock
+        assertFalse(mgr.isLockedBy(RESOURCE_B, OWNER1));
+    }
+
+    @Test
+    public void testIsLockedBy_LockedButNotOwner() {
+        mgr.lock(RESOURCE_A, OWNER1, null);
+
+        // different owner
+        assertFalse(mgr.isLockedBy(RESOURCE_A, OWNER2));
+    }
+
+    @Test
+    public void testMultiThreaded() throws InterruptedException {
+        int nthreads = 10;
+        int nlocks = 100;
+
+        LinkedList<Thread> threads = new LinkedList<>();
+
+        String[] resources = {RESOURCE_A, RESOURCE_B};
+
+        AtomicInteger nfail = new AtomicInteger(0);
+
+        CountDownLatch stopper = new CountDownLatch(1);
+        CountDownLatch completed = new CountDownLatch(nthreads);
+
+        for (int x = 0; x < nthreads; ++x) {
+            String owner = "owner." + x;
+
+            Thread t = new Thread() {
+                @Override
+                public void run() {
+
+                    for (int y = 0; y < nlocks; ++y) {
+                        String res = resources[y % resources.length];
+
+                        try {
+                            // some locks will be acquired, some denied
+                            mgr.lock(res, owner, null).get();
+
+                            // do some "work"
+                            stopper.await(1L, TimeUnit.MILLISECONDS);
+
+                            mgr.unlock(res, owner);
+
+                        } catch (CancellationException | ExecutionException e) {
+                            nfail.incrementAndGet();
+
+                        } catch (InterruptedException expected) {
+                            Thread.currentThread().interrupt();
+                            break;
+                        }
+                    }
+
+                    completed.countDown();
+                }
+            };
+
+            t.setDaemon(true);
+            threads.add(t);
+        }
+
+        // start the threads
+        for (Thread t : threads) {
+            t.start();
+        }
+
+        // wait for them to complete
+        completed.await(5000L, TimeUnit.SECONDS);
+
+        // stop the threads from sleeping
+        stopper.countDown();
+
+        completed.await(1L, TimeUnit.SECONDS);
+
+        // interrupt those that are still alive
+        for (Thread t : threads) {
+            if (t.isAlive()) {
+                t.interrupt();
+            }
+        }
+
+        assertEquals(0, nfail.get());
+    }
+
+}
diff --git a/policy-core/src/test/java/org/onap/policy/drools/core/lock/TestUtils.java b/policy-core/src/test/java/org/onap/policy/drools/core/lock/TestUtils.java
new file mode 100644
index 00000000..2e353936
--- /dev/null
+++ b/policy-core/src/test/java/org/onap/policy/drools/core/lock/TestUtils.java
@@ -0,0 +1,59 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * 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.drools.core.lock;
+
+public class TestUtils {
+
+    /**
+     * Invokes a function that is expected to throw an exception.
+     * 
+     * @param clazz class of exception that is expected
+     * @param func
+     * @return
+     */
+    public static <T> T expectException(Class<T> clazz, VoidFunction func) {
+        try {
+            func.apply(null);
+            throw new AssertionError("missing exception");
+
+        } catch (Exception e) {
+            try {
+                return clazz.cast(e);
+
+            } catch (ClassCastException e2) {
+                throw new AssertionError("incorrect exception type", e2);
+            }
+        }
+    }
+
+    /**
+     * Void function that may throw an exception.
+     */
+    @FunctionalInterface
+    public static interface VoidFunction {
+
+        /**
+         * 
+         * @param arg always {@code null}
+         */
+        public void apply(Void arg) throws Exception;
+    }
+}