diff --git a/java/com/google/gerrit/plugins/codeowners/backend/BackendModule.java b/java/com/google/gerrit/plugins/codeowners/backend/BackendModule.java
index adccb0f..a93c20d 100644
--- a/java/com/google/gerrit/plugins/codeowners/backend/BackendModule.java
+++ b/java/com/google/gerrit/plugins/codeowners/backend/BackendModule.java
@@ -22,6 +22,7 @@
 import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.ServerInitiated;
 import com.google.gerrit.server.UserInitiated;
+import com.google.gerrit.server.restapi.change.OnPostReview;
 import com.google.inject.Provides;
 
 /** Guice module to bind code owner backends. */
@@ -45,6 +46,7 @@
     install(new CodeOwnerSubmitRule.Module());
 
     DynamicSet.bind(binder(), ExceptionHook.class).to(CodeOwnersExceptionHook.class);
+    DynamicSet.bind(binder(), OnPostReview.class).to(CodeOwnersOnPostReview.class);
   }
 
   @Provides
diff --git a/java/com/google/gerrit/plugins/codeowners/backend/CodeOwnersOnPostReview.java b/java/com/google/gerrit/plugins/codeowners/backend/CodeOwnersOnPostReview.java
new file mode 100644
index 0000000..376c483
--- /dev/null
+++ b/java/com/google/gerrit/plugins/codeowners/backend/CodeOwnersOnPostReview.java
@@ -0,0 +1,238 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// 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 com.google.gerrit.plugins.codeowners.backend;
+
+import static com.google.common.base.Preconditions.checkState;
+import static com.google.common.collect.ImmutableList.toImmutableList;
+import static java.util.Comparator.comparing;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.flogger.FluentLogger;
+import com.google.gerrit.entities.Account;
+import com.google.gerrit.entities.PatchSet;
+import com.google.gerrit.extensions.restapi.ResourceConflictException;
+import com.google.gerrit.plugins.codeowners.JgitPath;
+import com.google.gerrit.plugins.codeowners.api.CodeOwnerStatus;
+import com.google.gerrit.plugins.codeowners.config.CodeOwnersPluginConfiguration;
+import com.google.gerrit.plugins.codeowners.config.RequiredApproval;
+import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.notedb.ChangeNotes;
+import com.google.gerrit.server.patch.PatchListNotAvailableException;
+import com.google.gerrit.server.restapi.change.OnPostReview;
+import com.google.gerrit.server.util.LabelVote;
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+/**
+ * Callback that is invoked on post review.
+ *
+ * <p>If a code owner approval was added, removed or changed, include in the change message that is
+ * being posted on vote, which of the files:
+ *
+ * <ul>
+ *   <li>are approved now
+ *   <li>are no longer approved
+ *   <li>are still approved
+ * </ul>
+ */
+@Singleton
+class CodeOwnersOnPostReview implements OnPostReview {
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  private final CodeOwnersPluginConfiguration codeOwnersPluginConfiguration;
+  private final CodeOwnerApprovalCheck codeOwnerApprovalCheck;
+
+  @Inject
+  CodeOwnersOnPostReview(
+      CodeOwnersPluginConfiguration codeOwnersPluginConfiguration,
+      CodeOwnerApprovalCheck codeOwnerApprovalCheck) {
+    this.codeOwnersPluginConfiguration = codeOwnersPluginConfiguration;
+    this.codeOwnerApprovalCheck = codeOwnerApprovalCheck;
+  }
+
+  @Override
+  public Optional<String> getChangeMessageAddOn(
+      IdentifiedUser user,
+      ChangeNotes changeNotes,
+      PatchSet patchSet,
+      Map<String, Short> oldApprovals,
+      Map<String, Short> approvals) {
+    // code owner approvals are only computed for the current patch set
+    if (!changeNotes.getChange().currentPatchSetId().equals(patchSet.id())) {
+      return Optional.empty();
+    }
+
+    RequiredApproval requiredApproval =
+        codeOwnersPluginConfiguration.getRequiredApproval(changeNotes.getProjectName());
+
+    if (!oldApprovals.containsKey(requiredApproval.labelType().getName())) {
+      // if oldApprovals doesn't contain the label, the label was not changed
+      return Optional.empty();
+    }
+
+    return buildMessageForCodeOwnerApproval(
+        user, changeNotes, patchSet, oldApprovals, approvals, requiredApproval);
+  }
+
+  private Optional<String> buildMessageForCodeOwnerApproval(
+      IdentifiedUser user,
+      ChangeNotes changeNotes,
+      PatchSet patchSet,
+      Map<String, Short> oldApprovals,
+      Map<String, Short> approvals,
+      RequiredApproval requiredApproval) {
+    LabelVote newVote = getNewVote(requiredApproval, approvals);
+
+    ImmutableList<Path> ownedPaths = getOwnedPaths(changeNotes, user.getAccountId());
+    if (ownedPaths.isEmpty()) {
+      // the user doesn't own any of the modified paths
+      return Optional.empty();
+    }
+
+    boolean hasImplicitApprovalByUser =
+        codeOwnersPluginConfiguration.areImplicitApprovalsEnabled(changeNotes.getProjectName())
+            && patchSet.uploader().equals(user.getAccountId());
+
+    boolean noLongerExplicitlyApproved = false;
+    StringBuilder message = new StringBuilder();
+    if (isCodeOwnerApprovalNewlyApplied(requiredApproval, oldApprovals, newVote)) {
+      if (hasImplicitApprovalByUser) {
+        message.append(
+            String.format(
+                "By voting %s the following files are now explicitly code-owner approved by %s:\n",
+                newVote, user.getName()));
+      } else {
+        message.append(
+            String.format(
+                "By voting %s the following files are now code-owner approved by %s:\n",
+                newVote, user.getName()));
+      }
+    } else if (isCodeOwnerApprovalRemoved(requiredApproval, oldApprovals, newVote)) {
+      if (newVote.value() == 0) {
+        if (hasImplicitApprovalByUser) {
+          noLongerExplicitlyApproved = true;
+          message.append(
+              String.format(
+                  "By removing the %s vote the following files are no longer explicitly code-owner"
+                      + " approved by %s:\n",
+                  newVote.label(), user.getName()));
+        } else {
+          message.append(
+              String.format(
+                  "By removing the %s vote the following files are no longer code-owner approved"
+                      + " by %s:\n",
+                  newVote.label(), user.getName()));
+        }
+      } else {
+        if (hasImplicitApprovalByUser) {
+          noLongerExplicitlyApproved = true;
+          message.append(
+              String.format(
+                  "By voting %s the following files are no longer explicitly code-owner approved by"
+                      + " %s:\n",
+                  newVote, user.getName()));
+        } else {
+          message.append(
+              String.format(
+                  "By voting %s the following files are no longer code-owner approved by %s:\n",
+                  newVote, user.getName()));
+        }
+      }
+    } else if (isCodeOwnerApprovalUpOrDowngraded(requiredApproval, oldApprovals, newVote)) {
+      if (hasImplicitApprovalByUser) {
+        message.append(
+            String.format(
+                "By voting %s the following files are still explicitly code-owner approved by"
+                    + " %s:\n",
+                newVote, user.getName()));
+      } else {
+        message.append(
+            String.format(
+                "By voting %s the following files are still code-owner approved by %s:\n",
+                newVote, user.getName()));
+      }
+    } else {
+      return Optional.empty();
+    }
+
+    ownedPaths.forEach(path -> message.append(String.format("* %s\n", JgitPath.of(path).get())));
+
+    if (hasImplicitApprovalByUser && noLongerExplicitlyApproved) {
+      message.append(
+          String.format(
+              "\nThe listed files are still implicitly approved by %s.\n", user.getName()));
+    }
+
+    return Optional.of(message.toString());
+  }
+
+  private boolean isCodeOwnerApprovalNewlyApplied(
+      RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
+    String labelName = requiredApproval.labelType().getName();
+    return oldApprovals.get(labelName) < requiredApproval.value()
+        && newVote.value() >= requiredApproval.value();
+  }
+
+  private boolean isCodeOwnerApprovalRemoved(
+      RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
+    String labelName = requiredApproval.labelType().getName();
+    return oldApprovals.get(labelName) >= requiredApproval.value()
+        && newVote.value() < requiredApproval.value();
+  }
+
+  private boolean isCodeOwnerApprovalUpOrDowngraded(
+      RequiredApproval requiredApproval, Map<String, Short> oldApprovals, LabelVote newVote) {
+    String labelName = requiredApproval.labelType().getName();
+    return oldApprovals.get(labelName) >= requiredApproval.value()
+        && newVote.value() >= requiredApproval.value();
+  }
+
+  private LabelVote getNewVote(RequiredApproval requiredApproval, Map<String, Short> approvals) {
+    String labelName = requiredApproval.labelType().getName();
+    checkState(
+        approvals.containsKey(labelName),
+        "expected that approval on label %s exists (approvals = %s)",
+        labelName,
+        approvals);
+    return LabelVote.create(labelName, approvals.get(labelName));
+  }
+
+  private ImmutableList<Path> getOwnedPaths(ChangeNotes changeNotes, Account.Id accountId) {
+    try {
+      return codeOwnerApprovalCheck
+          .getFileStatusesForAccount(changeNotes, accountId)
+          .flatMap(
+              fileCodeOwnerStatus ->
+                  Stream.of(
+                          fileCodeOwnerStatus.newPathStatus(), fileCodeOwnerStatus.oldPathStatus())
+                      .filter(Optional::isPresent)
+                      .map(Optional::get))
+          .filter(PathCodeOwnerStatus -> PathCodeOwnerStatus.status() == CodeOwnerStatus.APPROVED)
+          .map(PathCodeOwnerStatus::path)
+          .sorted(comparing(Path::toString))
+          .collect(toImmutableList());
+    } catch (IOException | ResourceConflictException | PatchListNotAvailableException e) {
+      logger.atSevere().withCause(e).log(
+          "Failed to compute owned paths of change %s for account %s",
+          changeNotes.getChangeId(), accountId.get());
+      return ImmutableList.of();
+    }
+  }
+}
diff --git a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnersOnPostReviewIT.java b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnersOnPostReviewIT.java
new file mode 100644
index 0000000..f3507a9
--- /dev/null
+++ b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnersOnPostReviewIT.java
@@ -0,0 +1,449 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// 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 com.google.gerrit.plugins.codeowners.acceptance.api;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Iterables;
+import com.google.gerrit.acceptance.config.GerritConfig;
+import com.google.gerrit.extensions.api.changes.ReviewInput;
+import com.google.gerrit.extensions.common.ChangeMessageInfo;
+import com.google.gerrit.extensions.common.LabelDefinitionInput;
+import com.google.gerrit.plugins.codeowners.acceptance.AbstractCodeOwnersIT;
+import java.util.Collection;
+import org.junit.Test;
+
+/**
+ * Acceptance test for {@code com.google.gerrit.plugins.codeowners.backend.CodeOwnersOnPostReview}.
+ */
+public class CodeOwnersOnPostReviewIT extends AbstractCodeOwnersIT {
+  @Test
+  public void changeMessageListsNewlyApprovedPaths() throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange("Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: Code-Review+1\n\n"
+                    + "By voting Code-Review+1 the following files are now code-owner approved by"
+                    + " %s:\n"
+                    + "* %s\n",
+                admin.fullName(), path));
+  }
+
+  @Test
+  public void changeMessageListsPathsThatAreStillApproved() throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange("Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    // Upgrade the approval from Code-Review+1 to Code-Review+2
+    approve(changeId);
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: Code-Review+2\n\n"
+                    + "By voting Code-Review+2 the following files are still code-owner approved by"
+                    + " %s:\n"
+                    + "* %s\n",
+                admin.fullName(), path));
+  }
+
+  @Test
+  public void changeMessageListsPathsThatAreNoLongerApproved_voteRemoved() throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange("Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    // Remove the approval.
+    gApi.changes().id(changeId).current().review(new ReviewInput().label("Code-Review", 0));
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: -Code-Review\n\n"
+                    + "By removing the Code-Review vote the following files are no longer"
+                    + " code-owner approved by %s:\n"
+                    + "* %s\n",
+                admin.fullName(), path));
+  }
+
+  @Test
+  public void changeMessageListsPathsThatAreNoLongerApproved_voteChangedToNegativeValue()
+      throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange("Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    // Vote with a negative value.
+    gApi.changes().id(changeId).current().review(new ReviewInput().label("Code-Review", -1));
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: Code-Review-1\n\n"
+                    + "By voting Code-Review-1 the following files are no longer code-owner"
+                    + " approved by %s:\n"
+                    + "* %s\n",
+                admin.fullName(), path));
+  }
+
+  @Test
+  public void changeMessageListsOnlyApprovedPaths() throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path1 = "foo/bar.baz";
+    String path2 = "foo/baz.bar";
+    String changeId =
+        createChange(
+                "Test Change",
+                ImmutableMap.of(
+                    path1,
+                    "file content",
+                    path2,
+                    "file content",
+                    "bar/foo.baz",
+                    "file content",
+                    "bar/baz.foo",
+                    "file content"))
+            .getChangeId();
+
+    recommend(changeId);
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: Code-Review+1\n\n"
+                    + "By voting Code-Review+1 the following files are now code-owner approved by"
+                    + " %s:\n"
+                    + "* %s\n"
+                    + "* %s\n",
+                admin.fullName(), path1, path2));
+  }
+
+  @Test
+  public void changeMessageListsOnlyApprovedPaths_fileRenamed() throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    // createChangeWithFileRename creates a change with 2 patch sets
+    String oldPath = "foo/bar.baz";
+    String newPath = "bar/baz.bar";
+    String changeId = createChangeWithFileRename(oldPath, newPath);
+
+    recommend(changeId);
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 2: Code-Review+1\n\n"
+                    + "By voting Code-Review+1 the following files are now code-owner approved by"
+                    + " %s:\n"
+                    + "* %s\n",
+                admin.fullName(), oldPath));
+  }
+
+  @Test
+  public void changeMessageNotExtendedIfUserOwnsNoneOfTheFiles() throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String changeId =
+        createChange(
+                "Test Change",
+                ImmutableMap.of("bar/foo.baz", "file content", "bar/baz.foo", "file content"))
+            .getChangeId();
+
+    recommend(changeId);
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message).isEqualTo("Patch Set 1: Code-Review+1");
+  }
+
+  @Test
+  @GerritConfig(name = "plugin.code-owners.requiredApproval", value = "Owners-Approval+1")
+  public void changeMessageNotExtendedForNonCodeOwnerApproval() throws Exception {
+    LabelDefinitionInput input = new LabelDefinitionInput();
+    input.values = ImmutableMap.of("+1", "Owner Approval", " 0", "No Owner Approval");
+    gApi.projects().name(project.get()).label("Owners-Approval").create(input).get();
+
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String changeId =
+        createChange(
+                "Test Change",
+                ImmutableMap.of("bar/foo.baz", "file content", "bar/baz.foo", "file content"))
+            .getChangeId();
+
+    recommend(changeId);
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message).isEqualTo("Patch Set 1: Code-Review+1");
+  }
+
+  @Test
+  @GerritConfig(name = "plugin.code-owners.enableImplicitApprovals", value = "true")
+  public void changeMessageListsNewlyApprovedPathsIfTheyWereAlreadyImplicitlyApproved()
+      throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange("Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: Code-Review+1\n\n"
+                    + "By voting Code-Review+1 the following files are now explicitly code-owner"
+                    + " approved by %s:\n"
+                    + "* %s\n",
+                admin.fullName(), path));
+  }
+
+  @Test
+  @GerritConfig(name = "plugin.code-owners.enableImplicitApprovals", value = "true")
+  public void changeMessageListsPathsThatAreNoLongerExplicitlyApproved_voteRemoved()
+      throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange("Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    // Remove the approval.
+    gApi.changes().id(changeId).current().review(new ReviewInput().label("Code-Review", 0));
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: -Code-Review\n\n"
+                    + "By removing the Code-Review vote the following files are no longer"
+                    + " explicitly code-owner approved by %s:\n"
+                    + "* %s\n"
+                    + "\n"
+                    + "The listed files are still implicitly approved by %s.\n",
+                admin.fullName(), path, admin.fullName()));
+  }
+
+  @Test
+  @GerritConfig(name = "plugin.code-owners.enableImplicitApprovals", value = "true")
+  public void changeMessageListsPathsThatAreNoLongerExplicitlyApproved_voteChangedToNegativeValue()
+      throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange("Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    // Vote with a negative value.
+    gApi.changes().id(changeId).current().review(new ReviewInput().label("Code-Review", -1));
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: Code-Review-1\n\n"
+                    + "By voting Code-Review-1 the following files are no longer explicitly"
+                    + " code-owner approved by %s:\n"
+                    + "* %s\n"
+                    + "\n"
+                    + "The listed files are still implicitly approved by %s.\n",
+                admin.fullName(), path, admin.fullName()));
+  }
+
+  @Test
+  @GerritConfig(name = "plugin.code-owners.enableImplicitApprovals", value = "true")
+  public void changeMessageListsNewlyApprovedPaths_noImplicitApprovalButImplicitApprovalsEnabled()
+      throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange(user, "Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: Code-Review+1\n\n"
+                    + "By voting Code-Review+1 the following files are now code-owner approved by"
+                    + " %s:\n"
+                    + "* %s\n",
+                admin.fullName(), path));
+  }
+
+  @Test
+  @GerritConfig(name = "plugin.code-owners.enableImplicitApprovals", value = "true")
+  public void
+      changeMessageListsPathsThatAreNoLongerApproved_voteRemoved_noImplicitApprovalButImplicitApprovalsEnabled()
+          throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange(user, "Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    // Remove the approval.
+    gApi.changes().id(changeId).current().review(new ReviewInput().label("Code-Review", 0));
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: -Code-Review\n\n"
+                    + "By removing the Code-Review vote the following files are no longer"
+                    + " code-owner approved by %s:\n"
+                    + "* %s\n",
+                admin.fullName(), path));
+  }
+
+  @Test
+  @GerritConfig(name = "plugin.code-owners.enableImplicitApprovals", value = "true")
+  public void
+      changeMessageListsPathsThatAreNoLongerApproved_voteChangedToNegativeValue_noImplicitApprovalButImplicitApprovalsEnabled()
+          throws Exception {
+    codeOwnerConfigOperations
+        .newCodeOwnerConfig()
+        .project(project)
+        .branch("master")
+        .folderPath("/foo/")
+        .addCodeOwnerEmail(admin.email())
+        .create();
+
+    String path = "foo/bar.baz";
+    String changeId = createChange(user, "Test Change", path, "file content").getChangeId();
+
+    recommend(changeId);
+
+    // Vote with a negative value.
+    gApi.changes().id(changeId).current().review(new ReviewInput().label("Code-Review", -1));
+
+    Collection<ChangeMessageInfo> messages = gApi.changes().id(changeId).get().messages;
+    assertThat(Iterables.getLast(messages).message)
+        .isEqualTo(
+            String.format(
+                "Patch Set 1: Code-Review-1\n\n"
+                    + "By voting Code-Review-1 the following files are no longer code-owner"
+                    + " approved by %s:\n"
+                    + "* %s\n",
+                admin.fullName(), path));
+  }
+}