HONEYCOMB-405 - Revert fix for indirect updates

If indirect update(delete+create) fails in a way, that delete passed,
but update part failed, delete part must be reverted

Moves reverter creation to MDTG and test cases related too it to
ModifiableDataTreeDelegatorRevertTest

Fixes tracking of allready processed changes by tracking them
from perspective of processModifications() method

Introduces UpdateFailedException as replacement
for BulkUpdateException(now thrown also for single updates)

Separates ReverterImpl from FlatWriterRegistry and ads unit tests

Change-Id: If0066d0716d9476be89b1d99985b6745becac15e
Signed-off-by: Jan Srnicek <jsrnicek@cisco.com>

6 files changed, 791 insertions, 167 deletions

diff --git a/infra/data-impl/src/main/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegator.java b/infra/data-impl/src/main/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegator.java
index 66dcbe5d9..e76c5b6e5 100644
--- a/infra/data-impl/src/main/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegator.java
+++ b/infra/data-impl/src/main/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegator.java
@@ -33,8 +33,12 @@ import io.fd.honeycomb.translate.util.TransactionMappingContext;
 import io.fd.honeycomb.translate.util.write.TransactionWriteContext;
 import io.fd.honeycomb.translate.write.DataObjectUpdate;
 import io.fd.honeycomb.translate.write.WriteContext;
+import io.fd.honeycomb.translate.write.registry.UpdateFailedException;
 import io.fd.honeycomb.translate.write.registry.WriterRegistry;
+import java.util.List;
 import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import org.opendaylight.controller.md.sal.common.api.data.TransactionCommitFailedException;
@@ -136,33 +140,37 @@ public final class ModifiableDataTreeDelegator extends ModifiableDataTreeManager
                     ((TransactionMappingContext) ctx.getMappingContext()).submit();
                 // Blocking on context data update
                 contextUpdateResult.checkedGet();
-
-            } catch (WriterRegistry.BulkUpdateException e) {
+            } catch (UpdateFailedException e) {
+                // TODO - HONEYCOMB-411
                 LOG.warn("Failed to apply all changes", e);
-                LOG.info("Trying to revert successful changes for current transaction");
-
-                try {
-                    // attempt revert with fresh context, to allow write logic used context-binded data
-                    e.revertChanges(getRevertTransactionContext(ctx.getMappingContext()));
-                    LOG.info("Changes successfully reverted");
-                } catch (WriterRegistry.Reverter.RevertFailedException revertFailedException) {
-                    // fail with failed revert
-                    LOG.error("Failed to revert successful(comitted) changes, failure occurred for: {}. State might be corrupted.",
-                            revertFailedException.getFailedUpdate(), revertFailedException);
-                    throw revertFailedException;
+                final List<DataObjectUpdate> processed = e.getProcessed();
+                if (processed.isEmpty()) {
+                    // nothing was processed, which means either very first operation failed, or it was single operation
+                    // update. In both cases, no revert is needed
+                    LOG.info("Nothing to revert");
+                    throw e;
+                } else {
+                    LOG.info("Trying to revert successful changes for current transaction");
+                    try {
+                        // attempt revert with fresh context, to allow write logic used context-binded data
+                        new Reverter(processed, writerRegistry)
+                                .revert(getRevertTransactionContext(ctx.getMappingContext()));
+                        LOG.info("Changes successfully reverted");
+                    } catch (Reverter.RevertFailedException revertFailedException) {
+                        // fail with failed revert
+                        LOG.error("Failed to revert successful(comitted) changes", revertFailedException);
+                        throw revertFailedException;
+                    }
                 }
                 // fail with success revert
                 // not passing the cause,its logged above and it would be logged after transaction
                 // ended again(prevent double logging of same error
-                throw new WriterRegistry.Reverter.RevertSuccessException(e.getUnrevertedSubtrees());
+                throw new Reverter.RevertSuccessException(getNonProcessedNodes(baUpdates, processed));
             } catch (TransactionCommitFailedException e) {
                 // TODO HONEYCOMB-162 revert should probably occur when context is not written successfully
                 final String msg = "Error while updating mapping context data";
                 LOG.error(msg, e);
                 throw new TranslationException(msg, e);
-            } catch (TranslationException e) {
-                LOG.error("Error while processing data change (updates={})", baUpdates, e);
-                throw e;
             } finally {
                 // Using finally instead of try-with-resources in order to leave ctx open for BulkUpdateException catch
                 // block. The context is needed there, but try-with-resources closes the resource before handling ex.
@@ -200,6 +208,14 @@ public final class ModifiableDataTreeDelegator extends ModifiableDataTreeManager
         }
     }
 
+    private static Set<InstanceIdentifier<?>> getNonProcessedNodes(final WriterRegistry.DataObjectUpdates allUpdates,
+                                                                   final List<DataObjectUpdate> alreadyProcessed) {
+        return allUpdates.getAllModifications().stream()
+                .filter(update -> !alreadyProcessed.contains(update))
+                .map(DataObjectUpdate::getId)
+                .collect(Collectors.toSet());
+    }
+
     @VisibleForTesting
     static WriterRegistry.DataObjectUpdates toBindingAware(
             final WriterRegistry registry,
diff --git a/infra/data-impl/src/main/java/io/fd/honeycomb/data/impl/Reverter.java b/infra/data-impl/src/main/java/io/fd/honeycomb/data/impl/Reverter.java
new file mode 100644
index 000000000..9c7262647
--- /dev/null
+++ b/infra/data-impl/src/main/java/io/fd/honeycomb/data/impl/Reverter.java
@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2017 Cisco and/or its affiliates.
+ *
+ * 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.
+ */
+
+package io.fd.honeycomb.data.impl;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static io.fd.honeycomb.translate.util.RWUtils.makeIidWildcarded;
+
+import com.google.common.annotations.Beta;
+import com.google.common.collect.LinkedHashMultimap;
+import com.google.common.collect.Multimap;
+import io.fd.honeycomb.translate.TranslationException;
+import io.fd.honeycomb.translate.write.DataObjectUpdate;
+import io.fd.honeycomb.translate.write.WriteContext;
+import io.fd.honeycomb.translate.write.registry.UpdateFailedException;
+import io.fd.honeycomb.translate.write.registry.WriterRegistry;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+import javax.annotation.Nonnull;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Takes list of changes, creates revert operations and writes them using writer registry
+ */
+final class Reverter {
+
+    private static final Logger LOG = LoggerFactory.getLogger(Reverter.class);
+
+    private final List<DataObjectUpdate> toBeReverted;
+    private final WriterRegistry writerRegistry;
+
+    /**
+     * @param toBeReverted   - list of changes in order they were processed, that should be reverted. Reverting order
+     *                       and data inside operations will be done by this reverter.
+     * @param writerRegistry - registry able to handle all nodes that should be reverted
+     */
+    Reverter(final List<DataObjectUpdate> toBeReverted,
+             final WriterRegistry writerRegistry) {
+        this.toBeReverted = toBeReverted;
+        this.writerRegistry = writerRegistry;
+    }
+
+    /**
+     * Reverts changes that were successfully applied during update before failure occurred. Changes are reverted in
+     * reverse order they were applied. Used {@code WriteContext} needs to be in non-closed state, creating fresh one
+     * for revert is recommended, same way as for write, to allow {@code Reverter} use same logic as write.
+     *
+     * @param writeContext Non-closed {@code WriteContext} to be used by reverting logic
+     * @throws RevertFailedException if not all of applied changes were successfully reverted
+     */
+    void revert(@Nonnull final WriteContext writeContext) throws RevertFailedException {
+        checkNotNull(writeContext, "Cannot revert changes for null context");
+
+        // create list of changes in revert order, and than switch data inside these chagnes to create opposite operations
+        final WriterRegistry.DataObjectUpdates revertedAndMapped = revertAndMapProcessed(revertOrder(toBeReverted));
+
+        LOG.info("Attempting revert for changes: {}", revertedAndMapped);
+        try {
+            // Perform reversed bulk update without revert attempt
+            writerRegistry.processModifications(revertedAndMapped, writeContext);
+            LOG.info("Revert successful");
+        } catch (UpdateFailedException e) {
+            // some of revert operations failed
+            // throws exception with all revert operations that failed
+            LOG.error("Revert failed", e);
+            final Set<DataObjectUpdate> nonReverted = revertedAndMapped.getAllModifications();
+            nonReverted.removeAll(e.getProcessed());
+            throw new RevertFailedException(e.getFailed(), nonReverted, e);
+        } catch (Exception e) {
+            // any other unexpected error
+            LOG.error("Revert failed with unexpected error");
+            throw new RevertFailedException(e);
+        }
+    }
+
+    /**
+     * Switching before and after data for each update.
+     */
+    private WriterRegistry.DataObjectUpdates revertAndMapProcessed(final List<DataObjectUpdate> updates) {
+        // uses linked maps to preserve order of insertion
+        final Multimap<InstanceIdentifier<?>, DataObjectUpdate> updatesMap = LinkedHashMultimap.create();
+        final Multimap<InstanceIdentifier<?>, DataObjectUpdate.DataObjectDelete> deleteMap =
+                LinkedHashMultimap.create();
+
+        updates.stream()
+                .map(DataObjectUpdate::reverse)
+                .forEach(reversed -> {
+                    // putting under unkeyed identifier, to prevent failing of checkAllTypesCanBeHandled
+                    final InstanceIdentifier<?> wildcardedIid = makeIidWildcarded(reversed.getId());
+                    if (reversed.getDataAfter() == null) {
+                        deleteMap.put(wildcardedIid, DataObjectUpdate.DataObjectDelete.class.cast(reversed));
+                    } else {
+                        updatesMap.put(wildcardedIid, reversed);
+                    }
+                });
+        return new WriterRegistry.DataObjectUpdates(updatesMap, deleteMap);
+    }
+
+    private List<DataObjectUpdate> revertOrder(final List<DataObjectUpdate> processingOrdered) {
+        final List<DataObjectUpdate> copy = new ArrayList<>(processingOrdered);
+        Collections.reverse(copy);
+        return copy;
+    }
+
+    /**
+     * Thrown when some of the changes applied during update were not reverted.
+     */
+    @Beta
+    static class RevertFailedException extends TranslationException {
+
+        /**
+         * Constructs a RevertFailedException with the list of changes that were not reverted.
+         *
+         * @param cause      the cause of revert failure
+         * @param failed     node that failed to revert
+         * @param unreverted unreverted changes
+         */
+        RevertFailedException(@Nonnull final DataObjectUpdate failed,
+                              @Nonnull final Set<DataObjectUpdate> unreverted,
+                              @Nonnull final Exception cause) {
+            super("Unable to revert changes after failure. Revert failed for "
+                    + failed + " unreverted subtrees: " + unreverted, cause);
+        }
+
+        RevertFailedException(@Nonnull final Exception cause) {
+            super("Unexpected error while reverting", cause);
+        }
+    }
+
+    /**
+     * Thrown after bulk operation was successfully reverted, to maintain marking of transaction as failed,without
+     * double logging of cause of update fail(its logged before reverting in ModifiableDataTreeDelegator
+     */
+    @Beta
+    static class RevertSuccessException extends TranslationException {
+        private final Set<InstanceIdentifier<?>> failedIds;
+
+        /**
+         * Constructs an RevertSuccessException.
+         *
+         * @param failedIds instance identifiers of the data objects that were not processed during bulk update.
+         */
+        public RevertSuccessException(@Nonnull final Set<InstanceIdentifier<?>> failedIds) {
+            super("Bulk update failed for: " + failedIds);
+            this.failedIds = failedIds;
+        }
+
+        public Set<InstanceIdentifier<?>> getFailedIds() {
+            return failedIds;
+        }
+    }
+}
diff --git a/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorBaseTest.java b/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorBaseTest.java
new file mode 100644
index 000000000..5690e78c3
--- /dev/null
+++ b/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorBaseTest.java
@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2017 Cisco and/or its affiliates.
+ *
+ * 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.
+ */
+
+package io.fd.honeycomb.data.impl;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.google.common.util.concurrent.Futures;
+import io.fd.honeycomb.translate.write.DataObjectUpdate;
+import io.fd.honeycomb.translate.write.WriteContext;
+import io.fd.honeycomb.translate.write.registry.WriterRegistry;
+import java.util.AbstractMap;
+import java.util.Map;
+import org.junit.Before;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.opendaylight.controller.md.sal.binding.api.DataBroker;
+import org.opendaylight.mdsal.binding.dom.codec.api.BindingNormalizedNodeSerializer;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.opendaylight.yangtools.yang.common.QName;
+import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
+import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
+
+abstract class ModifiableDataTreeDelegatorBaseTest extends ModificationBaseTest {
+
+    @Mock
+    WriterRegistry writer;
+    @Mock
+    BindingNormalizedNodeSerializer serializer;
+    @Mock
+    org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification modification;
+    @Mock
+    DataBroker contextBroker;
+    @Mock
+    org.opendaylight.controller.md.sal.binding.api.ReadWriteTransaction tx;
+
+    @Captor
+    ArgumentCaptor<WriteContext> writeContextCaptor;
+
+    @Captor
+    ArgumentCaptor<WriterRegistry.DataObjectUpdates> updatesCaptor;
+
+    final InstanceIdentifier<?> DEFAULT_ID = InstanceIdentifier.create(DataObject.class);
+    final DataObject DEFAULT_DATA_OBJECT = mockDataObject("serialized", DataObject.class);
+
+    DataTree dataTree;
+    ModifiableDataTreeManager configDataTree;
+    DataObjectUpdate update = DataObjectUpdate.create(DEFAULT_ID, null, DEFAULT_DATA_OBJECT);
+
+    @Before
+    public void setup() throws Exception {
+        MockitoAnnotations.initMocks(this);
+        dataTree = getDataTree();
+        when(contextBroker.newReadWriteTransaction()).thenReturn(tx);
+        when(tx.submit()).thenReturn(Futures.immediateCheckedFuture(null));
+
+        when(serializer.fromYangInstanceIdentifier(any(YangInstanceIdentifier.class)))
+                .thenReturn(((InstanceIdentifier) DEFAULT_ID));
+        final Map.Entry<InstanceIdentifier<?>, DataObject> parsed =
+                new AbstractMap.SimpleEntry<>(DEFAULT_ID, DEFAULT_DATA_OBJECT);
+        when(serializer.fromNormalizedNode(any(YangInstanceIdentifier.class), any(NormalizedNode.class)))
+                .thenReturn(parsed);
+
+        configDataTree = new ModifiableDataTreeDelegator(serializer, dataTree, getSchemaCtx(), writer, contextBroker);
+
+        additionalSetup();
+    }
+
+    void additionalSetup() throws Exception {
+    }
+
+    private static DataObject mockDataObject(final String name, final Class<? extends DataObject> classToMock) {
+        final DataObject dataBefore = mock(classToMock, name);
+        doReturn(classToMock).when(dataBefore).getImplementedInterface();
+        return dataBefore;
+    }
+
+    abstract static class DataObject1 implements DataObject {
+    }
+
+    abstract static class DataObject2 implements DataObject {
+    }
+
+    abstract static class DataObject3 implements DataObject {
+    }
+
+    <D extends DataObject> D mockDataObject(final YangInstanceIdentifier yid1,
+                                                    final InstanceIdentifier iid1,
+                                                    final NormalizedNode nn1B,
+                                                    final Class<D> type) {
+        final D do1B = mock(type);
+        when(serializer.fromNormalizedNode(yid1, nn1B)).thenReturn(new AbstractMap.SimpleEntry<>(iid1, do1B));
+        return do1B;
+    }
+
+    NormalizedNode mockNormalizedNode(final QName nn1) {
+        final NormalizedNode nn1B = mock(NormalizedNode.class);
+        when(nn1B.getNodeType()).thenReturn(nn1);
+        return nn1B;
+    }
+
+    InstanceIdentifier mockIid(final YangInstanceIdentifier yid1,
+                                       final Class<? extends DataObject> type) {
+        final InstanceIdentifier iid1 = InstanceIdentifier.create(type);
+        when(serializer.fromYangInstanceIdentifier(yid1)).thenReturn(iid1);
+        return iid1;
+    }
+
+    YangInstanceIdentifier mockYid(final QName nn1) {
+        final YangInstanceIdentifier yid1 = mock(YangInstanceIdentifier.class);
+        when(yid1.getLastPathArgument()).thenReturn(new YangInstanceIdentifier.NodeIdentifier(nn1));
+        return yid1;
+    }
+}
diff --git a/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorRevertTest.java b/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorRevertTest.java
new file mode 100644
index 000000000..2787cdf1f
--- /dev/null
+++ b/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorRevertTest.java
@@ -0,0 +1,257 @@
+/*
+ * Copyright (c) 2017 Cisco and/or its affiliates.
+ *
+ * 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.
+ */
+
+package io.fd.honeycomb.data.impl;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import io.fd.honeycomb.data.DataModification;
+import io.fd.honeycomb.translate.TranslationException;
+import io.fd.honeycomb.translate.write.DataObjectUpdate;
+import io.fd.honeycomb.translate.write.WriteContext;
+import io.fd.honeycomb.translate.write.registry.UpdateFailedException;
+import io.fd.honeycomb.translate.write.registry.WriterRegistry;
+import java.util.Collections;
+import java.util.List;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.opendaylight.yangtools.yang.data.api.schema.MapNode;
+
+public class ModifiableDataTreeDelegatorRevertTest extends ModifiableDataTreeDelegatorBaseTest {
+
+    /**
+     * Test scenario when commit fails, but there's nothing to revert because very first crud operation failed
+     */
+    @Test
+    public void testCommitFailedNoRevert() throws Exception {
+        final MapNode nestedList = getNestedList("listEntry", "listValue");
+
+        // Fail on update:
+        final TranslationException failedOnUpdateException = new TranslationException("update failed");
+        doThrow(new UpdateFailedException(failedOnUpdateException, Collections.emptyList(), update))// fail on update
+                .when(writer)
+                .processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
+
+        try {
+            // Run the test
+            final DataModification dataModification = configDataTree.newModification();
+            dataModification.write(NESTED_LIST_ID, nestedList);
+            dataModification.validate();
+            dataModification.commit();
+            fail("UpdateFailedException was expected");
+        } catch (UpdateFailedException e) {
+            // writer was called only one for update, and it was only one operation so no revert needed
+            // exception was just rethrown
+            verify(writer).processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
+            assertEquals(e.getFailed().getId(), DEFAULT_ID);
+            assertTrue(e.getProcessed().isEmpty());
+        }
+    }
+
+    /**
+     * Test whether
+     *  - Correct operations were invoked(when creating and reverting)
+     *  - Create and revert both failed
+     *  - Correct exception has been thrown
+     * Steps:
+     * - Prepares state with nested list written
+     * - Attempts to rewrite that list with new list with value with different key
+     * - Simulates fail(both on modification and revert)
+     * - Checks modifications
+     * Asserts
+     * - index 0 - Represents create of original data
+     * - index 1 - Represents override with new list(fails)(include delete of data created by index 0 and create of new)
+     * - index 2 - Represents revert of removal of original data
+     */
+    @Test
+    public void testCommitWithRevertFailed() throws Exception {
+        // configure initial state
+        final MapNode originalList = getNestedList("listEntryOriginal", "listValueOriginal");
+
+        final DataModification preModification = configDataTree.newModification();
+        preModification.write(NESTED_LIST_ID, originalList);
+        preModification.validate();
+        preModification.commit();
+
+        // then test
+        final MapNode nestedList = getNestedList("listEntry", "listValueNew");
+
+        // Fail on update:
+        final TranslationException failedOnUpdateException = new TranslationException("update failed");
+        final DataObjectUpdate.DataObjectDelete mockRevertData = mock(DataObjectUpdate.DataObjectDelete.class);
+        final DataObjectUpdate.DataObjectDelete mockRevertDataReverted = mock(DataObjectUpdate.DataObjectDelete.class);
+        when(mockRevertData.getId()).thenReturn((InstanceIdentifier) InstanceIdentifier.create(DataObject.class));
+        when(mockRevertDataReverted.getId())
+                .thenReturn((InstanceIdentifier) InstanceIdentifier.create(DataObject.class));
+        when(mockRevertData.getDataBefore()).thenReturn(DEFAULT_DATA_OBJECT);// to simulate that delete of original data
+        //should be reverted
+        when(mockRevertDataReverted.getDataAfter())
+                .thenReturn(DEFAULT_DATA_OBJECT);// to simulate that delete of original data
+        //should be reverted
+        when(mockRevertData.reverse()).thenReturn(mockRevertDataReverted);
+
+        final UpdateFailedException cause =
+                new UpdateFailedException(failedOnUpdateException,
+                        Collections.singletonList(mockRevertData),//fail on new one
+                        update);
+        doThrow(cause)
+                .when(writer)
+                .processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
+
+        try {
+            // Run the test
+            final DataModification dataModification = configDataTree.newModification();
+            dataModification.write(NESTED_LIST_ID, nestedList);
+            dataModification.validate();
+            dataModification.commit();
+            fail("WriterRegistry.Reverter.RevertFailedException was expected");
+        } catch (Reverter.RevertFailedException e) {
+            assertRewriteModificationWithRevert(writer, updatesCaptor, DEFAULT_DATA_OBJECT);
+            assertEquals(cause, e.getCause());
+        }
+    }
+
+    /**
+     * Test whether
+     *  - Correct operations were invoked(when creating and reverting)
+     *  - Create failed and revert passed
+     *  - Correct exception has been thrown
+     * Steps:
+     * - Prepares state with nested list written
+     * - Attempts to rewrite that list with new list with value with different key
+     * - Simulates fail on create
+     * - Passes on revert
+     * - Checks modifications
+     * Asserts
+     * - index 0 - Represents create of original data
+     * - index 1 - Represents override with new list(fails)(include delete of data created by index 0 and create of new)
+     * - index 2 - Represents revert of removal of original data
+     */
+    @Test
+    public void testCommitWithRevertSuccessfull() throws Exception {
+        // configure initial state
+        final MapNode originalList = getNestedList("listEntryOriginal", "listValueOriginal");
+
+        final DataModification preModification = configDataTree.newModification();
+        preModification.write(NESTED_LIST_ID, originalList);
+        preModification.validate();
+        preModification.commit();
+
+        // then test
+        final MapNode nestedList = getNestedList("listEntry", "listValueNew");
+
+        // Fail on update:
+        final TranslationException failedOnUpdateException = new TranslationException("update failed");
+        final DataObjectUpdate.DataObjectDelete mockRevertData = mock(DataObjectUpdate.DataObjectDelete.class);
+        final DataObjectUpdate.DataObjectDelete mockRevertDataReverted = mock(DataObjectUpdate.DataObjectDelete.class);
+        when(mockRevertData.getId()).thenReturn((InstanceIdentifier) InstanceIdentifier.create(DataObject.class));
+        when(mockRevertDataReverted.getId())
+                .thenReturn((InstanceIdentifier) InstanceIdentifier.create(DataObject.class));
+        when(mockRevertData.getDataBefore()).thenReturn(DEFAULT_DATA_OBJECT);// to simulate that delete of original data
+        //should be reverted
+        when(mockRevertDataReverted.getDataAfter())
+                .thenReturn(DEFAULT_DATA_OBJECT);// to simulate that delete of original data
+        //should be reverted
+        when(mockRevertData.reverse()).thenReturn(mockRevertDataReverted);
+
+        final UpdateFailedException cause =
+                new UpdateFailedException(failedOnUpdateException,
+                        Collections.singletonList(mockRevertData),//fail on new one
+                        update);
+        doThrow(cause) // fails on create
+                .doNothing()//to pass on revert
+                .when(writer)
+                .processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
+
+        try {
+            // Run the test
+            final DataModification dataModification = configDataTree.newModification();
+            dataModification.write(NESTED_LIST_ID, nestedList);
+            dataModification.validate();
+            dataModification.commit();
+            fail("WriterRegistry.Reverter.RevertFailedException was expected");
+        } catch (Reverter.RevertSuccessException e) {
+            assertRewriteModificationWithRevert(writer, updatesCaptor, DEFAULT_DATA_OBJECT);
+            assertNull(e.getCause());
+        }
+    }
+
+    private static void assertRewriteModificationWithRevert(final WriterRegistry writer,
+                                                            final ArgumentCaptor<WriterRegistry.DataObjectUpdates> updatesCaptor,
+                                                            final DataObject DEFAULT_DATA_OBJECT)
+            throws TranslationException {
+        verify(writer, times(3)).processModifications(updatesCaptor.capture(), any(WriteContext.class));
+        final List<WriterRegistry.DataObjectUpdates> allUpdates = updatesCaptor.getAllValues();
+        assertEquals(3, allUpdates.size());
+
+        // represent create of original data
+        final WriterRegistry.DataObjectUpdates originalCreate = allUpdates.get(0);
+        assertContainsOnlySingleUpdate(originalCreate);
+
+        final DataObjectUpdate createOriginalData = originalCreate.getUpdates().values().iterator().next();
+        assertCreateWithData(createOriginalData, DEFAULT_DATA_OBJECT);
+
+        // delete of original data was successful
+        // create of new data - failed
+        final WriterRegistry.DataObjectUpdates originalDelete = allUpdates.get(1);
+        assertConstainsSingleUpdateAndDelete(originalDelete);
+
+        final DataObjectUpdate.DataObjectDelete deleteOriginalData =
+                originalDelete.getDeletes().values().iterator().next();
+        assertDeleteWithData(deleteOriginalData, DEFAULT_DATA_OBJECT);
+
+        final DataObjectUpdate newCreate = originalDelete.getUpdates().values().iterator().next();
+        assertCreateWithData(newCreate, DEFAULT_DATA_OBJECT);
+
+        final WriterRegistry.DataObjectUpdates revert = allUpdates.get(2);
+        assertContainsOnlySingleUpdate(revert);
+    }
+
+    private static void assertDeleteWithData(final DataObjectUpdate.DataObjectDelete deleteOriginalData,
+                                             final DataObject DEFAULT_DATA_OBJECT) {
+        assertNull(deleteOriginalData.getDataAfter());
+        assertEquals(DEFAULT_DATA_OBJECT, deleteOriginalData.getDataBefore());
+    }
+
+    private static void assertCreateWithData(final DataObjectUpdate newCreate, final DataObject DEFAULT_DATA_OBJECT) {
+        assertNull(newCreate.getDataBefore());
+        assertEquals(DEFAULT_DATA_OBJECT, newCreate.getDataAfter());
+    }
+
+    private static void assertContainsOnlySingleUpdate(final WriterRegistry.DataObjectUpdates originalCreate) {
+        assertThat(originalCreate.getDeletes().size(), is(0));
+        assertThat(originalCreate.getUpdates().size(), is(1));
+    }
+
+    private static void assertConstainsSingleUpdateAndDelete(final WriterRegistry.DataObjectUpdates originalDelete) {
+        assertThat(originalDelete.getDeletes().size(), is(1));
+        assertThat(originalDelete.getUpdates().size(), is(1));
+    }
+
+}
diff --git a/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorTest.java b/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorTest.java
index ccd35a93d..56c0c610f 100644
--- a/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorTest.java
+++ b/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ModifiableDataTreeDelegatorTest.java
@@ -22,84 +22,32 @@ import static org.hamcrest.CoreMatchers.is;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.eq;
-import static org.mockito.Mockito.doReturn;
-import static org.mockito.Mockito.doThrow;
-import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
-import static org.mockito.MockitoAnnotations.initMocks;
 
 import com.google.common.base.Optional;
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.ImmutableMultimap;
 import com.google.common.collect.Multimap;
 import com.google.common.util.concurrent.CheckedFuture;
-import com.google.common.util.concurrent.Futures;
 import io.fd.honeycomb.data.DataModification;
-import io.fd.honeycomb.translate.TranslationException;
 import io.fd.honeycomb.translate.write.DataObjectUpdate;
 import io.fd.honeycomb.translate.write.WriteContext;
 import io.fd.honeycomb.translate.write.registry.WriterRegistry;
-import java.util.AbstractMap;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
-import org.junit.Before;
 import org.junit.Test;
-import org.mockito.ArgumentCaptor;
-import org.mockito.Captor;
-import org.mockito.Mock;
-import org.opendaylight.controller.md.sal.binding.api.DataBroker;
 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
-import org.opendaylight.mdsal.binding.dom.codec.api.BindingNormalizedNodeSerializer;
-import org.opendaylight.yangtools.yang.binding.DataObject;
 import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
 import org.opendaylight.yangtools.yang.common.QName;
 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
 import org.opendaylight.yangtools.yang.data.api.schema.ContainerNode;
 import org.opendaylight.yangtools.yang.data.api.schema.MapNode;
 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
-import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
 
-public class ModifiableDataTreeDelegatorTest extends ModificationBaseTest {
-
-    @Mock
-    private WriterRegistry writer;
-    @Mock
-    private BindingNormalizedNodeSerializer serializer;
-    private DataTree dataTree;
-    @Mock
-    private org.opendaylight.yangtools.yang.data.api.schema.tree.DataTreeModification modification;
-    @Mock
-    private DataBroker contextBroker;
-    @Mock
-    private org.opendaylight.controller.md.sal.binding.api.ReadWriteTransaction tx;
-
-    @Captor
-    private ArgumentCaptor<WriteContext> writeContextCaptor;
-
-    private ModifiableDataTreeManager configDataTree;
-    private final DataObjectUpdate update = DataObjectUpdate.create(DEFAULT_ID, null, DEFAULT_DATA_OBJECT);
-
-    static final InstanceIdentifier<?> DEFAULT_ID = InstanceIdentifier.create(DataObject.class);
-    static DataObject DEFAULT_DATA_OBJECT = mockDataObject("serialized", DataObject.class);
-
-    @Before
-    public void setUp() throws Exception {
-        initMocks(this);
-        dataTree = getDataTree();
-        when(contextBroker.newReadWriteTransaction()).thenReturn(tx);
-        when(tx.submit()).thenReturn(Futures.immediateCheckedFuture(null));
-
-        when(serializer.fromYangInstanceIdentifier(any(YangInstanceIdentifier.class))).thenReturn(((InstanceIdentifier) DEFAULT_ID));
-        final Map.Entry<InstanceIdentifier<?>, DataObject> parsed = new AbstractMap.SimpleEntry<>(DEFAULT_ID, DEFAULT_DATA_OBJECT);
-        when(serializer.fromNormalizedNode(any(YangInstanceIdentifier.class), any(NormalizedNode.class))).thenReturn(parsed);
-
-        configDataTree = new ModifiableDataTreeDelegator(serializer, dataTree, getSchemaCtx(), writer, contextBroker);
-    }
+public class ModifiableDataTreeDelegatorTest extends ModifiableDataTreeDelegatorBaseTest {
 
     @Test
     public void testRead() throws Exception {
@@ -134,70 +82,6 @@ public class ModifiableDataTreeDelegatorTest extends ModificationBaseTest {
         assertEquals(nestedList, dataTree.takeSnapshot().readNode(NESTED_LIST_ID).get());
     }
 
-    private static DataObject mockDataObject(final String name, final Class<? extends DataObject> classToMock) {
-        final DataObject dataBefore = mock(classToMock, name);
-        doReturn(classToMock).when(dataBefore).getImplementedInterface();
-        return dataBefore;
-    }
-
-    @Test
-    public void testCommitUndoSuccessful() throws Exception {
-        final MapNode nestedList = getNestedList("listEntry", "listValue");
-
-        // Fail on update:
-        final WriterRegistry.Reverter reverter = mock(WriterRegistry.Reverter.class);
-        final TranslationException failedOnUpdateException = new TranslationException("update failed");
-        doThrow(new WriterRegistry.BulkUpdateException(DEFAULT_ID, update, Collections.singleton(DEFAULT_ID), reverter, failedOnUpdateException))
-                .when(writer).processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
-
-        try {
-            // Run the test
-            final DataModification dataModification = configDataTree.newModification();
-            dataModification.write(NESTED_LIST_ID, nestedList);
-            dataModification.validate();
-            dataModification.commit();
-            fail("WriterRegistry.RevertSuccessException was expected");
-        } catch (WriterRegistry.Reverter.RevertSuccessException e) {
-            verify(writer).processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
-            assertThat(e.getFailedIds(), hasItem(DEFAULT_ID));
-            verify(reverter).revert(any(WriteContext.class));
-        }
-    }
-
-    @Test
-    public void testCommitUndoFailed() throws Exception {
-        final MapNode nestedList = getNestedList("listEntry", "listValue");
-
-        // Fail on update:
-        final WriterRegistry.Reverter reverter = mock(WriterRegistry.Reverter.class);
-        final TranslationException failedOnUpdateException = new TranslationException("update failed");
-        final WriterRegistry.BulkUpdateException bulkFailEx =
-                new WriterRegistry.BulkUpdateException(DEFAULT_ID, update, Collections.singleton(DEFAULT_ID), reverter,
-                        failedOnUpdateException);
-        doThrow(bulkFailEx).when(writer).processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
-
-        // Fail on revert:
-        doThrow(new WriterRegistry.Reverter.RevertFailedException(bulkFailEx))
-                .when(reverter).revert(any(WriteContext.class));
-
-        try {
-            // Run the test
-            final DataModification dataModification = configDataTree.newModification();
-            dataModification.write(NESTED_LIST_ID, nestedList);
-            dataModification.validate();
-            dataModification.commit();
-            fail("WriterRegistry.Reverter.RevertFailedException was expected");
-        } catch (WriterRegistry.Reverter.RevertFailedException e) {
-            verify(writer).processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
-            verify(reverter).revert(any(WriteContext.class));
-            assertEquals(bulkFailEx, e.getCause());
-        }
-    }
-
-    private abstract static class DataObject1 implements DataObject {}
-    private abstract static class DataObject2 implements DataObject {}
-    private abstract static class DataObject3 implements DataObject {}
-
     @Test
     public void testToBindingAware() throws Exception {
         when(serializer.fromNormalizedNode(any(YangInstanceIdentifier.class), eq(null))).thenReturn(null);
@@ -214,7 +98,7 @@ public class ModifiableDataTreeDelegatorTest extends ModificationBaseTest {
         // create
         final QName nn2 = QName.create("namespace", "nn1");
         final YangInstanceIdentifier yid2 = mockYid(nn2);
-        final InstanceIdentifier iid2 = mockIid(yid2, DataObject2.class);;
+        final InstanceIdentifier iid2 = mockIid(yid2, DataObject2.class);
         final NormalizedNode nn2A = mockNormalizedNode(nn2);
         final DataObject2 do2A = mockDataObject(yid2, iid2, nn2A, DataObject2.class);
         biNodes.put(yid2, NormalizedNodeUpdate.create(yid2, null, nn2A));
@@ -226,7 +110,7 @@ public class ModifiableDataTreeDelegatorTest extends ModificationBaseTest {
         final NormalizedNode nn3B = mockNormalizedNode(nn3);
         final DataObject3 do3B = mockDataObject(yid3, iid3, nn3B, DataObject3.class);
         final NormalizedNode nn3A = mockNormalizedNode(nn3);
-        final DataObject3 do3A = mockDataObject(yid3, iid3, nn3A, DataObject3.class);;
+        final DataObject3 do3A = mockDataObject(yid3, iid3, nn3A, DataObject3.class);
         biNodes.put(yid3, NormalizedNodeUpdate.create(yid3, nn3B, nn3A));
 
         final WriterRegistry.DataObjectUpdates dataObjectUpdates =
@@ -262,7 +146,7 @@ public class ModifiableDataTreeDelegatorTest extends ModificationBaseTest {
         // create
         final QName nn2 = QName.create("namespace", "nn1");
         final YangInstanceIdentifier yid2 = mockYid(nn2);
-        final InstanceIdentifier iid2 = mockIid(yid2, DataObject2.class);;
+        final InstanceIdentifier iid2 = mockIid(yid2, DataObject2.class);
         final NormalizedNode nn2A = mockNormalizedNode(nn2);
         final DataObject2 do2A = mockDataObject(yid2, iid2, nn2A, DataObject2.class);
         biNodes.put(yid2, NormalizedNodeUpdate.create(yid2, null, nn2A));
@@ -274,7 +158,7 @@ public class ModifiableDataTreeDelegatorTest extends ModificationBaseTest {
         final NormalizedNode nn3B = mockNormalizedNode(nn3);
         final DataObject3 do3B = mockDataObject(yid3, iid3, nn3B, DataObject3.class);
         final NormalizedNode nn3A = mockNormalizedNode(nn3);
-        final DataObject3 do3A = mockDataObject(yid3, iid3, nn3A, DataObject3.class);;
+        final DataObject3 do3A = mockDataObject(yid3, iid3, nn3A, DataObject3.class);
         biNodes.put(yid3, NormalizedNodeUpdate.create(yid3, nn3B, nn3A));
 
         final WriterRegistry.DataObjectUpdates dataObjectUpdates =
@@ -289,39 +173,11 @@ public class ModifiableDataTreeDelegatorTest extends ModificationBaseTest {
                 ((DataObjectUpdate.DataObjectDelete) DataObjectUpdate.create(iid3, do3B, null))));
 
         assertThat(dataObjectUpdates.getUpdates().size(), is(2));
-        assertThat(dataObjectUpdates.getUpdates().keySet(), hasItems( (InstanceIdentifier<?>) iid2, (InstanceIdentifier<?>) iid3));
+        assertThat(dataObjectUpdates.getUpdates().keySet(), hasItems((InstanceIdentifier<?>) iid2, (InstanceIdentifier<?>) iid3));
         assertThat(dataObjectUpdates.getUpdates().values(), hasItems(
                 DataObjectUpdate.create(iid2, null, do2A),
                 DataObjectUpdate.create(iid3, null, do3A)));
 
         assertThat(dataObjectUpdates.getTypeIntersection().size(), is(3));
     }
-
-    private <D extends DataObject> D mockDataObject(final YangInstanceIdentifier yid1,
-                                       final InstanceIdentifier iid1,
-                                       final NormalizedNode nn1B,
-                                       final Class<D> type) {
-        final D do1B = mock(type);
-        when(serializer.fromNormalizedNode(yid1, nn1B)).thenReturn(new AbstractMap.SimpleEntry<>(iid1, do1B));
-        return do1B;
-    }
-
-    private NormalizedNode mockNormalizedNode(final QName nn1) {
-        final NormalizedNode nn1B = mock(NormalizedNode.class);
-        when(nn1B.getNodeType()).thenReturn(nn1);
-        return nn1B;
-    }
-
-    private InstanceIdentifier mockIid(final YangInstanceIdentifier yid1,
-                                       final Class<? extends DataObject> type) {
-        final InstanceIdentifier iid1 = InstanceIdentifier.create(type);
-        when(serializer.fromYangInstanceIdentifier(yid1)).thenReturn(iid1);
-        return iid1;
-    }
-
-    private YangInstanceIdentifier mockYid(final QName nn1) {
-        final YangInstanceIdentifier yid1 = mock(YangInstanceIdentifier.class);
-        when(yid1.getLastPathArgument()).thenReturn(new YangInstanceIdentifier.NodeIdentifier(nn1));
-        return yid1;
-    }
 }
diff --git a/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ReverterTest.java b/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ReverterTest.java
new file mode 100644
index 000000000..db3fdbaf5
--- /dev/null
+++ b/infra/data-impl/src/test/java/io/fd/honeycomb/data/impl/ReverterTest.java
@@ -0,0 +1,192 @@
+/*
+ * Copyright (c) 2017 Cisco and/or its affiliates.
+ *
+ * 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.
+ */
+
+package io.fd.honeycomb.data.impl;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import com.google.common.collect.ImmutableList;
+import io.fd.honeycomb.translate.TranslationException;
+import io.fd.honeycomb.translate.write.DataObjectUpdate;
+import io.fd.honeycomb.translate.write.WriteContext;
+import io.fd.honeycomb.translate.write.registry.UpdateFailedException;
+import io.fd.honeycomb.translate.write.registry.WriterRegistry;
+import java.util.Collections;
+import java.util.Iterator;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Captor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+public class ReverterTest {
+
+    private static final InstanceIdentifier<DataObject> IID_0 = InstanceIdentifier.create(DataObject.class);
+    private static final InstanceIdentifier<DataObject1> IID_1 = InstanceIdentifier.create(DataObject1.class);
+    private static final InstanceIdentifier<DataObject2> IID_2 = InstanceIdentifier.create(DataObject2.class);
+
+    @Mock
+    private WriterRegistry registry;
+
+    @Mock
+    private WriteContext writeContext;
+
+    @Captor
+    private ArgumentCaptor<WriterRegistry.DataObjectUpdates> updateCaptor;
+
+    @Before
+    public void init() {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    @Test
+    public void revertSingle() throws Exception {
+        final DataObjectUpdate create = DataObjectUpdate.create(IID_0, null, mock(DataObject.class));
+
+        new Reverter(ImmutableList.of(create), registry).revert(writeContext);
+        assertSingleRevert(create);
+    }
+
+    @Test
+    public void revertSingleFailed() throws TranslationException {
+        final DataObjectUpdate create = DataObjectUpdate.create(IID_0, null, mock(DataObject.class));
+        final UpdateFailedException ex =
+                new UpdateFailedException(new IllegalStateException(), Collections.emptyList(), create);
+        doThrow(ex).when(registry)
+                .processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
+
+        try {
+            new Reverter(ImmutableList.of(create), registry).revert(writeContext);
+        } catch (Reverter.RevertFailedException e) {
+            assertEquals(ex, e.getCause());
+            assertSingleRevert(create);
+            return;
+        }
+        fail("Reverter.RevertFailedException was expected");
+    }
+
+
+    @Test
+    public void revertSingleFailedWithUnexpectedEx() throws TranslationException {
+        final DataObjectUpdate create = DataObjectUpdate.create(IID_0, null, mock(DataObject.class));
+        final IllegalStateException ex = new IllegalStateException();
+        doThrow(ex).when(registry)
+                .processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
+
+        try {
+            new Reverter(ImmutableList.of(create), registry).revert(writeContext);
+        } catch (Reverter.RevertFailedException e) {
+            assertEquals(ex, e.getCause());
+            assertSingleRevert(create);
+            return;
+        }
+        fail("IllegalStateException was expected");
+    }
+
+
+    @Test
+    public void revertMultiple() throws Exception {
+        final DataObjectUpdate create = DataObjectUpdate.create(IID_0, null, mock(DataObject.class));
+        final DataObjectUpdate update =
+                DataObjectUpdate.create(IID_1, mock(DataObject1.class), mock(DataObject1.class));
+        final DataObjectUpdate delete = DataObjectUpdate.create(IID_2, mock(DataObject2.class), null);
+
+        new Reverter(ImmutableList.of(create, update, delete), registry).revert(writeContext);
+        assertMultiRevert(create, update, delete);
+    }
+
+
+    @Test
+    public void revertMultipleFailed() throws Exception {
+        final DataObjectUpdate create = DataObjectUpdate.create(IID_0, null, mock(DataObject.class));
+        final DataObjectUpdate update =
+                DataObjectUpdate.create(IID_1, mock(DataObject1.class), mock(DataObject1.class));
+        final DataObjectUpdate delete = DataObjectUpdate.create(IID_2, mock(DataObject2.class), null);
+
+        final UpdateFailedException ex =
+                new UpdateFailedException(new IllegalStateException(), ImmutableList.of(create, update), create);
+        doThrow(ex).when(registry)
+                .processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
+
+        try {
+            new Reverter(ImmutableList.of(create, update, delete), registry).revert(writeContext);
+        } catch (Reverter.RevertFailedException e) {
+            assertEquals(ex, e.getCause());
+            assertMultiRevert(create, update, delete);
+            return;
+        }
+        fail("Reverter.RevertFailedException was expected");
+    }
+
+    @Test
+    public void revertMultipleFailedWithUnnexpectedException() throws Exception {
+        final DataObjectUpdate create = DataObjectUpdate.create(IID_0, null, mock(DataObject.class));
+        final DataObjectUpdate update =
+                DataObjectUpdate.create(IID_1, mock(DataObject1.class), mock(DataObject1.class));
+        final DataObjectUpdate delete = DataObjectUpdate.create(IID_2, mock(DataObject2.class), null);
+
+        final IllegalStateException ex = new IllegalStateException();
+        doThrow(ex).when(registry)
+                .processModifications(any(WriterRegistry.DataObjectUpdates.class), any(WriteContext.class));
+
+        try {
+            new Reverter(ImmutableList.of(create, update, delete), registry).revert(writeContext);
+        } catch (Reverter.RevertFailedException e) {
+            assertEquals(ex, e.getCause());
+            assertMultiRevert(create, update, delete);
+            return;
+        }
+        fail("IllegalStateException was expected");
+    }
+
+
+    private void assertSingleRevert(final DataObjectUpdate create) throws TranslationException {
+        verify(registry, times(1)).processModifications(updateCaptor.capture(), eq(writeContext));
+        final WriterRegistry.DataObjectUpdates updates = updateCaptor.getValue();
+        assertTrue(updates.getDeletes().containsValue(create.reverse()));
+        assertTrue(updates.getUpdates().isEmpty());
+    }
+
+    private void assertMultiRevert(final DataObjectUpdate create, final DataObjectUpdate update,
+                                   final DataObjectUpdate delete) throws TranslationException {
+        verify(registry, times(1)).processModifications(updateCaptor.capture(), eq(writeContext));
+        final WriterRegistry.DataObjectUpdates updates = updateCaptor.getValue();
+        final Iterator<DataObjectUpdate.DataObjectDelete> deletesIterator = updates.getDeletes().values().iterator();
+        final Iterator<DataObjectUpdate> updatesIterator = updates.getUpdates().values().iterator();
+
+        assertEquals(updatesIterator.next(), delete.reverse());
+        assertEquals(updatesIterator.next(), update.reverse());
+        assertEquals(deletesIterator.next(), create.reverse());
+    }
+
+
+    private interface DataObject1 extends DataObject {
+    }
+
+    private interface DataObject2 extends DataObject {
+    }
+}
\ No newline at end of file