diff --git a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnersPluginConfigValidatorIT.java b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnersPluginConfigValidatorIT.java
index b0caf0a..af8ba2e 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnersPluginConfigValidatorIT.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/CodeOwnersPluginConfigValidatorIT.java
@@ -20,7 +20,6 @@
 import static com.google.gerrit.extensions.client.ListChangesOption.CURRENT_REVISION;
 import static com.google.gerrit.plugins.codeowners.testing.RequiredApprovalSubject.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
@@ -46,6 +45,7 @@
 import com.google.gerrit.plugins.codeowners.backend.config.StatusConfig;
 import com.google.gerrit.plugins.codeowners.backend.proto.ProtoBackend;
 import com.google.gerrit.plugins.codeowners.common.MergeCommitStrategy;
+import com.google.gerrit.truth.OptionalSubject;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevObject;
@@ -257,7 +257,8 @@
 
     PushResult r = pushRefsMetaConfig();
     assertThat(r.getRemoteUpdate(RefNames.REFS_CONFIG).getStatus()).isEqualTo(Status.OK);
-    assertThat(codeOwnersPluginConfiguration.getProjectConfig(project).getPathExpressions("master"))
+    OptionalSubject.assertThat(
+            codeOwnersPluginConfiguration.getProjectConfig(project).getPathExpressions("master"))
         .value()
         .isEqualTo(PathExpressions.GLOB);
   }
@@ -276,7 +277,8 @@
 
     PushResult r = pushRefsMetaConfig();
     assertThat(r.getRemoteUpdate(RefNames.REFS_CONFIG).getStatus()).isEqualTo(Status.OK);
-    assertThat(codeOwnersPluginConfiguration.getProjectConfig(project).getPathExpressions("master"))
+    OptionalSubject.assertThat(
+            codeOwnersPluginConfiguration.getProjectConfig(project).getPathExpressions("master"))
         .value()
         .isEqualTo(PathExpressions.GLOB);
   }
diff --git a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/PutCodeOwnerProjectConfigIT.java b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/PutCodeOwnerProjectConfigIT.java
index e632f2a..ddddf39 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/PutCodeOwnerProjectConfigIT.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/acceptance/api/PutCodeOwnerProjectConfigIT.java
@@ -19,7 +19,6 @@
 import static com.google.gerrit.plugins.codeowners.testing.RequiredApprovalSubject.assertThat;
 import static com.google.gerrit.server.project.ProjectCache.illegalState;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
@@ -44,6 +43,7 @@
 import com.google.gerrit.plugins.codeowners.common.MergeCommitStrategy;
 import com.google.gerrit.server.project.ProjectState;
 import com.google.gerrit.server.restapi.project.DeleteRef;
+import com.google.gerrit.truth.OptionalSubject;
 import com.google.inject.Inject;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.junit.Before;
@@ -181,7 +181,8 @@
 
   @Test
   public void setFileExtension() throws Exception {
-    assertThat(codeOwnersPluginConfiguration.getProjectConfig(project).getFileExtension())
+    OptionalSubject.assertThat(
+            codeOwnersPluginConfiguration.getProjectConfig(project).getFileExtension())
         .isEmpty();
 
     CodeOwnerProjectConfigInput input = new CodeOwnerProjectConfigInput();
@@ -189,14 +190,16 @@
     CodeOwnerProjectConfigInfo updatedConfig =
         projectCodeOwnersApiFactory.project(project).updateConfig(input);
     assertThat(updatedConfig.general.fileExtension).isEqualTo("foo");
-    assertThat(codeOwnersPluginConfiguration.getProjectConfig(project).getFileExtension())
+    OptionalSubject.assertThat(
+            codeOwnersPluginConfiguration.getProjectConfig(project).getFileExtension())
         .value()
         .isEqualTo("foo");
 
     input.fileExtension = "";
     updatedConfig = projectCodeOwnersApiFactory.project(project).updateConfig(input);
     assertThat(updatedConfig.general.fileExtension).isNull();
-    assertThat(codeOwnersPluginConfiguration.getProjectConfig(project).getFileExtension())
+    OptionalSubject.assertThat(
+            codeOwnersPluginConfiguration.getProjectConfig(project).getFileExtension())
         .isEmpty();
   }
 
@@ -406,7 +409,8 @@
 
   @Test
   public void setOverrideInfoUrl() throws Exception {
-    assertThat(codeOwnersPluginConfiguration.getProjectConfig(project).getOverrideInfoUrl())
+    OptionalSubject.assertThat(
+            codeOwnersPluginConfiguration.getProjectConfig(project).getOverrideInfoUrl())
         .isEmpty();
 
     CodeOwnerProjectConfigInput input = new CodeOwnerProjectConfigInput();
@@ -414,20 +418,22 @@
     CodeOwnerProjectConfigInfo updatedConfig =
         projectCodeOwnersApiFactory.project(project).updateConfig(input);
     assertThat(updatedConfig.general.overrideInfoUrl).isEqualTo("http://foo.bar");
-    assertThat(codeOwnersPluginConfiguration.getProjectConfig(project).getOverrideInfoUrl())
+    OptionalSubject.assertThat(
+            codeOwnersPluginConfiguration.getProjectConfig(project).getOverrideInfoUrl())
         .value()
         .isEqualTo("http://foo.bar");
 
     input.overrideInfoUrl = "";
     updatedConfig = projectCodeOwnersApiFactory.project(project).updateConfig(input);
     assertThat(updatedConfig.general.overrideInfoUrl).isNull();
-    assertThat(codeOwnersPluginConfiguration.getProjectConfig(project).getOverrideInfoUrl())
+    OptionalSubject.assertThat(
+            codeOwnersPluginConfiguration.getProjectConfig(project).getOverrideInfoUrl())
         .isEmpty();
   }
 
   @Test
   public void setInvalidCodeOwnerConfigInfoUrl() throws Exception {
-    assertThat(
+    OptionalSubject.assertThat(
             codeOwnersPluginConfiguration
                 .getProjectConfig(project)
                 .getInvalidCodeOwnerConfigInfoUrl())
@@ -438,7 +444,7 @@
     CodeOwnerProjectConfigInfo updatedConfig =
         projectCodeOwnersApiFactory.project(project).updateConfig(input);
     assertThat(updatedConfig.general.invalidCodeOwnerConfigInfoUrl).isEqualTo("http://foo.bar");
-    assertThat(
+    OptionalSubject.assertThat(
             codeOwnersPluginConfiguration
                 .getProjectConfig(project)
                 .getInvalidCodeOwnerConfigInfoUrl())
@@ -448,7 +454,7 @@
     input.invalidCodeOwnerConfigInfoUrl = "";
     updatedConfig = projectCodeOwnersApiFactory.project(project).updateConfig(input);
     assertThat(updatedConfig.general.invalidCodeOwnerConfigInfoUrl).isNull();
-    assertThat(
+    OptionalSubject.assertThat(
             codeOwnersPluginConfiguration
                 .getProjectConfig(project)
                 .getInvalidCodeOwnerConfigInfoUrl())
diff --git a/javatests/com/google/gerrit/plugins/codeowners/acceptance/testsuite/CodeOwnerConfigOperationsImplTest.java b/javatests/com/google/gerrit/plugins/codeowners/acceptance/testsuite/CodeOwnerConfigOperationsImplTest.java
index 17e3ccd..d5e4dd5 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/acceptance/testsuite/CodeOwnerConfigOperationsImplTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/acceptance/testsuite/CodeOwnerConfigOperationsImplTest.java
@@ -17,7 +17,6 @@
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.plugins.codeowners.testing.CodeOwnerConfigSubject.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
@@ -37,6 +36,7 @@
 import com.google.gerrit.plugins.codeowners.backend.CodeOwners;
 import com.google.gerrit.plugins.codeowners.backend.CodeOwnersUpdate;
 import com.google.gerrit.server.ServerInitiated;
+import com.google.gerrit.truth.OptionalSubject;
 import com.google.inject.Key;
 import com.google.inject.Provider;
 import java.nio.file.Paths;
@@ -195,7 +195,7 @@
             .fileName("OWNERS_foo")
             .addCodeOwnerEmail(admin.email())
             .create();
-    assertThat(codeOwnerConfigKey.fileName()).value().isEqualTo("OWNERS_foo");
+    OptionalSubject.assertThat(codeOwnerConfigKey.fileName()).value().isEqualTo("OWNERS_foo");
     assertThat(getCodeOwnerConfigFromServer(codeOwnerConfigKey))
         .hasCodeOwnerSetsThat()
         .onlyElement()
@@ -441,7 +441,7 @@
     // was dropped.
     // Since this made the code owner config empty it caused a deletion of the code owner config
     // file.
-    assertThat(codeOwners.getFromCurrentRevision(codeOwnerConfig.key())).isEmpty();
+    OptionalSubject.assertThat(codeOwners.getFromCurrentRevision(codeOwnerConfig.key())).isEmpty();
   }
 
   @Test
@@ -507,7 +507,7 @@
         .update();
 
     // Removing all code owner sets leads to a deletion of the code owner config file.
-    assertThat(codeOwners.getFromCurrentRevision(codeOwnerConfig.key())).isEmpty();
+    OptionalSubject.assertThat(codeOwners.getFromCurrentRevision(codeOwnerConfig.key())).isEmpty();
   }
 
   @Test
@@ -570,7 +570,7 @@
         .update();
 
     // Removing all code owner sets leads to a deletion of the code owner config file.
-    assertThat(codeOwners.getFromCurrentRevision(codeOwnerConfig.key())).isEmpty();
+    OptionalSubject.assertThat(codeOwners.getFromCurrentRevision(codeOwnerConfig.key())).isEmpty();
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/ChangedFileTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/ChangedFileTest.java
index 2c84634..cc3a6e7 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/ChangedFileTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/ChangedFileTest.java
@@ -16,7 +16,6 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 import static org.mockito.Mockito.when;
 
 import com.google.gerrit.common.Nullable;
@@ -25,6 +24,7 @@
 import com.google.gerrit.plugins.codeowners.common.ChangedFile;
 import com.google.gerrit.server.patch.PatchListEntry;
 import com.google.gerrit.server.patch.filediff.FileDiffOutput;
+import com.google.gerrit.truth.OptionalSubject;
 import java.nio.file.Paths;
 import java.util.Optional;
 import org.eclipse.jgit.diff.DiffEntry;
@@ -48,14 +48,16 @@
   public void getNewPath_diffEntry() throws Exception {
     String newPath = "foo/bar/baz.txt";
     setupDiffEntry(newPath, /* oldPath= */ null, ChangeType.ADD);
-    assertThat(ChangedFile.create(diffEntry).newPath()).value().isEqualTo(Paths.get("/" + newPath));
+    OptionalSubject.assertThat(ChangedFile.create(diffEntry).newPath())
+        .value()
+        .isEqualTo(Paths.get("/" + newPath));
   }
 
   @Test
   public void getNewPath_patchListEntry() throws Exception {
     String newPath = "foo/bar/baz.txt";
     setupPatchListEntry(newPath, /* oldPath= */ null, Patch.ChangeType.ADDED);
-    assertThat(ChangedFile.create(patchListEntry).newPath())
+    OptionalSubject.assertThat(ChangedFile.create(patchListEntry).newPath())
         .value()
         .isEqualTo(Paths.get("/" + newPath));
   }
@@ -64,7 +66,7 @@
   public void getNewPath_fileDiffOutput() throws Exception {
     String newPath = "foo/bar/baz.txt";
     setupFileDiffOutput(newPath, /* oldPath= */ null, Patch.ChangeType.ADDED);
-    assertThat(ChangedFile.create(fileDiffOutput).newPath())
+    OptionalSubject.assertThat(ChangedFile.create(fileDiffOutput).newPath())
         .value()
         .isEqualTo(Paths.get("/" + newPath));
   }
@@ -72,19 +74,19 @@
   @Test
   public void getNewPathWhenNewPathIsNotSet_diffEntry() throws Exception {
     setupDiffEntry(/* newPath= */ null, /* oldPath= */ null, ChangeType.ADD);
-    assertThat(ChangedFile.create(diffEntry).newPath()).isEmpty();
+    OptionalSubject.assertThat(ChangedFile.create(diffEntry).newPath()).isEmpty();
   }
 
   @Test
   public void getNewPathWhenNewPathIsNotSet_patchListEntry() throws Exception {
     setupPatchListEntry(/* newPath= */ null, /* oldPath= */ null, Patch.ChangeType.ADDED);
-    assertThat(ChangedFile.create(patchListEntry).newPath()).isEmpty();
+    OptionalSubject.assertThat(ChangedFile.create(patchListEntry).newPath()).isEmpty();
   }
 
   @Test
   public void getNewPathWhenNewPathIsNotSet_fileDiffOutput() throws Exception {
     setupFileDiffOutput(/* newPath= */ null, /* oldPath= */ null, Patch.ChangeType.ADDED);
-    assertThat(ChangedFile.create(fileDiffOutput).newPath()).isEmpty();
+    OptionalSubject.assertThat(ChangedFile.create(fileDiffOutput).newPath()).isEmpty();
   }
 
   @Test
@@ -193,14 +195,16 @@
   public void getOldPath_diffEntry() throws Exception {
     String oldPath = "foo/bar/baz.txt";
     setupDiffEntry(/* newPath= */ null, oldPath, ChangeType.DELETE);
-    assertThat(ChangedFile.create(diffEntry).oldPath()).value().isEqualTo(Paths.get("/" + oldPath));
+    OptionalSubject.assertThat(ChangedFile.create(diffEntry).oldPath())
+        .value()
+        .isEqualTo(Paths.get("/" + oldPath));
   }
 
   @Test
   public void getOldPath_patchListEntry() throws Exception {
     String oldPath = "foo/bar/baz.txt";
     setupPatchListEntry(/* newPath= */ null, oldPath, Patch.ChangeType.DELETED);
-    assertThat(ChangedFile.create(patchListEntry).oldPath())
+    OptionalSubject.assertThat(ChangedFile.create(patchListEntry).oldPath())
         .value()
         .isEqualTo(Paths.get("/" + oldPath));
   }
@@ -209,7 +213,7 @@
   public void getOldPath_fileDiffOutput() throws Exception {
     String oldPath = "foo/bar/baz.txt";
     setupFileDiffOutput(/* newPath= */ null, oldPath, Patch.ChangeType.DELETED);
-    assertThat(ChangedFile.create(fileDiffOutput).oldPath())
+    OptionalSubject.assertThat(ChangedFile.create(fileDiffOutput).oldPath())
         .value()
         .isEqualTo(Paths.get("/" + oldPath));
   }
@@ -218,19 +222,19 @@
   public void getOldPathWhenOldPathIsNotSet_diffEntry() throws Exception {
     setupDiffEntry(/* newPath= */ null, /* oldPath= */ null, ChangeType.DELETE);
     when(diffEntry.getOldPath()).thenReturn(DiffEntry.DEV_NULL);
-    assertThat(ChangedFile.create(diffEntry).oldPath()).isEmpty();
+    OptionalSubject.assertThat(ChangedFile.create(diffEntry).oldPath()).isEmpty();
   }
 
   @Test
   public void getOldPathWhenOldPathIsNotSet_patchListEntry() throws Exception {
     setupPatchListEntry(/* newPath= */ null, /* oldPath= */ null, Patch.ChangeType.DELETED);
-    assertThat(ChangedFile.create(patchListEntry).oldPath()).isEmpty();
+    OptionalSubject.assertThat(ChangedFile.create(patchListEntry).oldPath()).isEmpty();
   }
 
   @Test
   public void getOldPathWhenOldPathIsNotSet_fileDiffOutput() throws Exception {
     setupFileDiffOutput(/* newPath= */ null, /* oldPath= */ null, Patch.ChangeType.DELETED);
-    assertThat(ChangedFile.create(fileDiffOutput).oldPath()).isEmpty();
+    OptionalSubject.assertThat(ChangedFile.create(fileDiffOutput).oldPath()).isEmpty();
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnersExceptionHookTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnersExceptionHookTest.java
index e1786d3..2f64510 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnersExceptionHookTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnersExceptionHookTest.java
@@ -15,13 +15,13 @@
 package com.google.gerrit.plugins.codeowners.backend;
 
 import static com.google.common.truth.Truth.assertThat;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 
 import com.google.common.collect.ImmutableList;
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.plugins.codeowners.acceptance.AbstractCodeOwnersTest;
 import com.google.gerrit.plugins.codeowners.backend.config.InvalidPluginConfigurationException;
 import com.google.gerrit.server.ExceptionHook.Status;
+import com.google.gerrit.truth.OptionalSubject;
 import java.nio.file.InvalidPathException;
 import java.util.Optional;
 import org.junit.Before;
@@ -114,29 +114,36 @@
   @Test
   public void getStatus() throws Exception {
     Status conflictStatus = Status.create(409, "Conflict");
-    assertThat(getStatus(newInvalidPluginConfigurationException()))
+    OptionalSubject.assertThat(getStatus(newInvalidPluginConfigurationException()))
         .value()
         .isEqualTo(conflictStatus);
-    assertThat(getStatus(newExceptionWithCause(newInvalidPluginConfigurationException())))
+    OptionalSubject.assertThat(
+            getStatus(newExceptionWithCause(newInvalidPluginConfigurationException())))
         .value()
         .isEqualTo(conflictStatus);
 
-    assertThat(getStatus(newInvalidCodeOwnerConfigException())).value().isEqualTo(conflictStatus);
-    assertThat(getStatus(newExceptionWithCause(newInvalidCodeOwnerConfigException())))
+    OptionalSubject.assertThat(getStatus(newInvalidCodeOwnerConfigException()))
+        .value()
+        .isEqualTo(conflictStatus);
+    OptionalSubject.assertThat(
+            getStatus(newExceptionWithCause(newInvalidCodeOwnerConfigException())))
         .value()
         .isEqualTo(conflictStatus);
 
-    assertThat(getStatus(newInvalidPathException())).value().isEqualTo(conflictStatus);
-    assertThat(getStatus(newExceptionWithCause(newInvalidPathException())))
+    OptionalSubject.assertThat(getStatus(newInvalidPathException()))
+        .value()
+        .isEqualTo(conflictStatus);
+    OptionalSubject.assertThat(getStatus(newExceptionWithCause(newInvalidPathException())))
         .value()
         .isEqualTo(conflictStatus);
 
-    assertThat(getStatus(new Exception())).isEmpty();
-    assertThat(getStatus(newExceptionWithCause(new Exception()))).isEmpty();
+    OptionalSubject.assertThat(getStatus(new Exception())).isEmpty();
+    OptionalSubject.assertThat(getStatus(newExceptionWithCause(new Exception()))).isEmpty();
 
-    assertThat(getStatus(CodeOwnersInternalServerErrorException.newInternalServerError("msg")))
+    OptionalSubject.assertThat(
+            getStatus(CodeOwnersInternalServerErrorException.newInternalServerError("msg")))
         .isEmpty();
-    assertThat(
+    OptionalSubject.assertThat(
             getStatus(
                 newExceptionWithCause(
                     CodeOwnersInternalServerErrorException.newInternalServerError("msg"))))
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnersTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnersTest.java
index fafc620..294dfd0 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnersTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/CodeOwnersTest.java
@@ -16,7 +16,6 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -26,6 +25,7 @@
 import com.google.gerrit.extensions.registration.PrivateInternals_DynamicMapImpl;
 import com.google.gerrit.extensions.registration.RegistrationHandle;
 import com.google.gerrit.plugins.codeowners.acceptance.AbstractCodeOwnersTest;
+import com.google.gerrit.truth.OptionalSubject;
 import com.google.inject.Key;
 import com.google.inject.util.Providers;
 import java.util.Optional;
@@ -92,7 +92,7 @@
     try (AutoCloseable registration = registerTestBackend("test-backend", codeOwnerBackendMock)) {
       Optional<CodeOwnerConfig> codeOwnerConfig =
           codeOwners.getFromCurrentRevision(codeOwnerConfigKey);
-      assertThat(codeOwnerConfig).value().isEqualTo(expectedCodeOwnersConfig);
+      OptionalSubject.assertThat(codeOwnerConfig).value().isEqualTo(expectedCodeOwnersConfig);
       verify(codeOwnerBackendMock).getCodeOwnerConfig(codeOwnerConfigKey, /* revision= */ null);
     }
   }
@@ -110,7 +110,7 @@
         .thenReturn(Optional.of(expectedCodeOwnersConfig));
     try (AutoCloseable registration = registerTestBackend("test-backend", codeOwnerBackendMock)) {
       Optional<CodeOwnerConfig> codeOwnerConfig = codeOwners.get(codeOwnerConfigKey, TEST_REVISION);
-      assertThat(codeOwnerConfig).value().isEqualTo(expectedCodeOwnersConfig);
+      OptionalSubject.assertThat(codeOwnerConfig).value().isEqualTo(expectedCodeOwnersConfig);
       verify(codeOwnerBackendMock).getCodeOwnerConfig(codeOwnerConfigKey, TEST_REVISION);
     }
   }
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/config/BackendConfigTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/config/BackendConfigTest.java
index dcc9cb3..fffc267 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/config/BackendConfigTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/config/BackendConfigTest.java
@@ -19,7 +19,6 @@
 import static com.google.gerrit.plugins.codeowners.backend.config.BackendConfig.KEY_PATH_EXPRESSIONS;
 import static com.google.gerrit.plugins.codeowners.backend.config.CodeOwnersPluginConfiguration.SECTION_CODE_OWNERS;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
@@ -32,6 +31,7 @@
 import com.google.gerrit.plugins.codeowners.backend.proto.ProtoBackend;
 import com.google.gerrit.server.git.validators.CommitValidationMessage;
 import com.google.gerrit.server.git.validators.ValidationMessage;
+import com.google.gerrit.truth.OptionalSubject;
 import org.eclipse.jgit.lib.Config;
 import org.junit.Before;
 import org.junit.Test;
@@ -65,7 +65,7 @@
 
   @Test
   public void getBackendForBranchWhenBackendIsNotSet() throws Exception {
-    assertThat(
+    OptionalSubject.assertThat(
             backendConfig.getBackendForBranch(
                 new Config(), BranchNameKey.create(project, "master")))
         .isEmpty();
@@ -79,7 +79,8 @@
         "refs/heads/master",
         KEY_BACKEND,
         CodeOwnerBackendId.FIND_OWNERS.getBackendId());
-    assertThat(backendConfig.getBackendForBranch(cfg, BranchNameKey.create(project, "master")))
+    OptionalSubject.assertThat(
+            backendConfig.getBackendForBranch(cfg, BranchNameKey.create(project, "master")))
         .value()
         .isInstanceOf(FindOwnersBackend.class);
   }
@@ -89,7 +90,8 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_CODE_OWNERS, "master", KEY_BACKEND, CodeOwnerBackendId.FIND_OWNERS.getBackendId());
-    assertThat(backendConfig.getBackendForBranch(cfg, BranchNameKey.create(project, "master")))
+    OptionalSubject.assertThat(
+            backendConfig.getBackendForBranch(cfg, BranchNameKey.create(project, "master")))
         .value()
         .isInstanceOf(FindOwnersBackend.class);
   }
@@ -131,7 +133,7 @@
 
   @Test
   public void getBackendForProjectWhenBackendIsNotSet() throws Exception {
-    assertThat(backendConfig.getBackendForProject(new Config(), project)).isEmpty();
+    OptionalSubject.assertThat(backendConfig.getBackendForProject(new Config(), project)).isEmpty();
   }
 
   @Test
@@ -139,7 +141,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_CODE_OWNERS, null, KEY_BACKEND, CodeOwnerBackendId.FIND_OWNERS.getBackendId());
-    assertThat(backendConfig.getBackendForProject(cfg, project))
+    OptionalSubject.assertThat(backendConfig.getBackendForProject(cfg, project))
         .value()
         .isInstanceOf(FindOwnersBackend.class);
   }
@@ -209,7 +211,7 @@
 
   @Test
   public void getPathExpressionsForBranchWhenPathExpressionsAreNotSet() throws Exception {
-    assertThat(
+    OptionalSubject.assertThat(
             backendConfig.getPathExpressionsForBranch(
                 new Config(), BranchNameKey.create(project, "master")))
         .isEmpty();
@@ -223,7 +225,7 @@
         "refs/heads/master",
         KEY_PATH_EXPRESSIONS,
         PathExpressions.GLOB.name());
-    assertThat(
+    OptionalSubject.assertThat(
             backendConfig.getPathExpressionsForBranch(cfg, BranchNameKey.create(project, "master")))
         .value()
         .isEqualTo(PathExpressions.GLOB);
@@ -233,7 +235,7 @@
   public void getPathExpressionsForBranchShortName() throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_CODE_OWNERS, "master", KEY_PATH_EXPRESSIONS, PathExpressions.GLOB.name());
-    assertThat(
+    OptionalSubject.assertThat(
             backendConfig.getPathExpressionsForBranch(cfg, BranchNameKey.create(project, "master")))
         .value()
         .isEqualTo(PathExpressions.GLOB);
@@ -243,7 +245,7 @@
   public void getPathExpressionsForBranchIfConfigIsInvalid() throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_CODE_OWNERS, "master", KEY_PATH_EXPRESSIONS, "INVALID");
-    assertThat(
+    OptionalSubject.assertThat(
             backendConfig.getPathExpressionsForBranch(cfg, BranchNameKey.create(project, "master")))
         .isEmpty();
   }
@@ -268,14 +270,15 @@
 
   @Test
   public void getPathExpressionsForProjectWhenBackendIsNotSet() throws Exception {
-    assertThat(backendConfig.getPathExpressionsForProject(new Config(), project)).isEmpty();
+    OptionalSubject.assertThat(backendConfig.getPathExpressionsForProject(new Config(), project))
+        .isEmpty();
   }
 
   @Test
   public void getPathExpressionsForProject() throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_CODE_OWNERS, null, KEY_PATH_EXPRESSIONS, PathExpressions.GLOB.name());
-    assertThat(backendConfig.getPathExpressionsForProject(cfg, project))
+    OptionalSubject.assertThat(backendConfig.getPathExpressionsForProject(cfg, project))
         .value()
         .isEqualTo(PathExpressions.GLOB);
   }
@@ -284,7 +287,7 @@
   public void getPathExpressionsForProjectIfConfigIsInvalid() throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_CODE_OWNERS, null, KEY_PATH_EXPRESSIONS, "INVALID");
-    assertThat(backendConfig.getPathExpressionsForProject(cfg, project)).isEmpty();
+    OptionalSubject.assertThat(backendConfig.getPathExpressionsForProject(cfg, project)).isEmpty();
   }
 
   @Test
@@ -307,19 +310,21 @@
 
   @Test
   public void getDefaultPathExpressions() throws Exception {
-    assertThat(backendConfig.getDefaultPathExpressions()).isEmpty();
+    OptionalSubject.assertThat(backendConfig.getDefaultPathExpressions()).isEmpty();
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.pathExpressions", value = "GLOB")
   public void getConfiguredDefaultPathExpressions() throws Exception {
-    assertThat(backendConfig.getDefaultPathExpressions()).value().isEqualTo(PathExpressions.GLOB);
+    OptionalSubject.assertThat(backendConfig.getDefaultPathExpressions())
+        .value()
+        .isEqualTo(PathExpressions.GLOB);
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.pathExpressions", value = "INVALID")
   public void getDefaultPathExpressionsIfConfigIsInvalid() throws Exception {
-    assertThat(backendConfig.getDefaultPathExpressions()).isEmpty();
+    OptionalSubject.assertThat(backendConfig.getDefaultPathExpressions()).isEmpty();
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginGlobalConfigSnapshotTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginGlobalConfigSnapshotTest.java
index 6a5c03d..e40d437 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginGlobalConfigSnapshotTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginGlobalConfigSnapshotTest.java
@@ -16,11 +16,11 @@
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 
 import com.google.gerrit.acceptance.config.GerritConfig;
 import com.google.gerrit.extensions.restapi.MethodNotAllowedException;
 import com.google.gerrit.plugins.codeowners.acceptance.AbstractCodeOwnersTest;
+import com.google.gerrit.truth.OptionalSubject;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -65,7 +65,7 @@
 
   @Test
   public void codeOwnerConfigCacheSizeIsLimitedByDefault() throws Exception {
-    assertThat(cfgSnapshot().getMaxCodeOwnerConfigCacheSize())
+    OptionalSubject.assertThat(cfgSnapshot().getMaxCodeOwnerConfigCacheSize())
         .value()
         .isEqualTo(CodeOwnersPluginGlobalConfigSnapshot.DEFAULT_MAX_CODE_OWNER_CONFIG_CACHE_SIZE);
   }
@@ -73,26 +73,28 @@
   @Test
   @GerritConfig(name = "plugin.code-owners.maxCodeOwnerConfigCacheSize", value = "0")
   public void codeOwnerConfigCacheSizeIsUnlimited() throws Exception {
-    assertThat(cfgSnapshot().getMaxCodeOwnerConfigCacheSize()).isEmpty();
+    OptionalSubject.assertThat(cfgSnapshot().getMaxCodeOwnerConfigCacheSize()).isEmpty();
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.maxCodeOwnerConfigCacheSize", value = "10")
   public void codeOwnerConfigCacheSizeIsLimited() throws Exception {
-    assertThat(cfgSnapshot().getMaxCodeOwnerConfigCacheSize()).value().isEqualTo(10);
+    OptionalSubject.assertThat(cfgSnapshot().getMaxCodeOwnerConfigCacheSize())
+        .value()
+        .isEqualTo(10);
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.maxCodeOwnerConfigCacheSize", value = "invalid")
   public void maxCodeOwnerConfigCacheSize_invalidConfig() throws Exception {
-    assertThat(cfgSnapshot().getMaxCodeOwnerConfigCacheSize())
+    OptionalSubject.assertThat(cfgSnapshot().getMaxCodeOwnerConfigCacheSize())
         .value()
         .isEqualTo(CodeOwnersPluginGlobalConfigSnapshot.DEFAULT_MAX_CODE_OWNER_CONFIG_CACHE_SIZE);
   }
 
   @Test
   public void codeOwnerCacheSizeIsLimitedByDefault() throws Exception {
-    assertThat(cfgSnapshot().getMaxCodeOwnerCacheSize())
+    OptionalSubject.assertThat(cfgSnapshot().getMaxCodeOwnerCacheSize())
         .value()
         .isEqualTo(CodeOwnersPluginGlobalConfigSnapshot.DEFAULT_MAX_CODE_OWNER_CACHE_SIZE);
   }
@@ -100,19 +102,19 @@
   @Test
   @GerritConfig(name = "plugin.code-owners.maxCodeOwnerCacheSize", value = "0")
   public void codeOwnerCacheSizeIsUnlimited() throws Exception {
-    assertThat(cfgSnapshot().getMaxCodeOwnerCacheSize()).isEmpty();
+    OptionalSubject.assertThat(cfgSnapshot().getMaxCodeOwnerCacheSize()).isEmpty();
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.maxCodeOwnerCacheSize", value = "10")
   public void codeOwnerCacheSizeIsLimited() throws Exception {
-    assertThat(cfgSnapshot().getMaxCodeOwnerCacheSize()).value().isEqualTo(10);
+    OptionalSubject.assertThat(cfgSnapshot().getMaxCodeOwnerCacheSize()).value().isEqualTo(10);
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.maxCodeOwnerCacheSize", value = "invalid")
   public void maxCodeOwnerCacheSize_invalidConfig() throws Exception {
-    assertThat(cfgSnapshot().getMaxCodeOwnerCacheSize())
+    OptionalSubject.assertThat(cfgSnapshot().getMaxCodeOwnerCacheSize())
         .value()
         .isEqualTo(CodeOwnersPluginGlobalConfigSnapshot.DEFAULT_MAX_CODE_OWNER_CACHE_SIZE);
   }
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginProjectConfigSnapshotTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginProjectConfigSnapshotTest.java
index 66649f9..77f79bf 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginProjectConfigSnapshotTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/config/CodeOwnersPluginProjectConfigSnapshotTest.java
@@ -19,7 +19,6 @@
 import static com.google.gerrit.plugins.codeowners.testing.CodeOwnerSetSubject.hasEmail;
 import static com.google.gerrit.plugins.codeowners.testing.RequiredApprovalSubject.assertThat;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
@@ -48,6 +47,7 @@
 import com.google.gerrit.plugins.codeowners.common.CodeOwnerConfigValidationPolicy;
 import com.google.gerrit.plugins.codeowners.common.MergeCommitStrategy;
 import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.truth.OptionalSubject;
 import com.google.inject.Inject;
 import com.google.inject.Key;
 import com.google.inject.util.Providers;
@@ -76,28 +76,28 @@
   @Test
   @GerritConfig(name = "plugin.code-owners.fileExtension", value = "foo")
   public void getFileExtensionIfNoneIsConfiguredOnProjectLevel() throws Exception {
-    assertThat(cfgSnapshot().getFileExtension()).value().isEqualTo("foo");
+    OptionalSubject.assertThat(cfgSnapshot().getFileExtension()).value().isEqualTo("foo");
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.fileExtension", value = "foo")
   public void fileExtensionOnProjectLevelOverridesDefaultFileExtension() throws Exception {
     configureFileExtension(project, "bar");
-    assertThat(cfgSnapshot().getFileExtension()).value().isEqualTo("bar");
+    OptionalSubject.assertThat(cfgSnapshot().getFileExtension()).value().isEqualTo("bar");
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.fileExtension", value = "foo")
   public void fileExtensionIsInheritedFromParentProject() throws Exception {
     configureFileExtension(allProjects, "bar");
-    assertThat(cfgSnapshot().getFileExtension()).value().isEqualTo("bar");
+    OptionalSubject.assertThat(cfgSnapshot().getFileExtension()).value().isEqualTo("bar");
   }
 
   @Test
   public void inheritedFileExtensionCanBeOverridden() throws Exception {
     configureFileExtension(allProjects, "foo");
     configureFileExtension(project, "bar");
-    assertThat(cfgSnapshot().getFileExtension()).value().isEqualTo("bar");
+    OptionalSubject.assertThat(cfgSnapshot().getFileExtension()).value().isEqualTo("bar");
   }
 
   @Test
@@ -1043,18 +1043,20 @@
 
   @Test
   public void getPathExpressionsForNonExistingBranch() throws Exception {
-    assertThat(cfgSnapshot().getPathExpressions("non-existing")).isEmpty();
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("non-existing")).isEmpty();
   }
 
   @Test
   public void getPathExpressionsWhenNoPathExpressionsAreConfigured() throws Exception {
-    assertThat(cfgSnapshot().getPathExpressions("master")).isEmpty();
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master")).isEmpty();
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.pathExpressions", value = "GLOB")
   public void getConfiguredPathExpressions() throws Exception {
-    assertThat(cfgSnapshot().getPathExpressions("master")).value().isEqualTo(PathExpressions.GLOB);
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
+        .value()
+        .isEqualTo(PathExpressions.GLOB);
   }
 
   @Test
@@ -1062,13 +1064,15 @@
       name = "plugin.code-owners.pathExpressions",
       value = "non-existing-path-expressions")
   public void getPathExpressionsIfNonExistingPathExpressionsAreConfigured() throws Exception {
-    assertThat(cfgSnapshot().getPathExpressions("master")).isEmpty();
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master")).isEmpty();
   }
 
   @Test
   public void getPathExpressionsConfiguredOnProjectLevel() throws Exception {
     configurePathExpressions(project, PathExpressions.GLOB.name());
-    assertThat(cfgSnapshot().getPathExpressions("master")).value().isEqualTo(PathExpressions.GLOB);
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
+        .value()
+        .isEqualTo(PathExpressions.GLOB);
   }
 
   @Test
@@ -1076,7 +1080,7 @@
   public void pathExpressionsConfiguredOnProjectLevelOverrideDefaultPathExpressions()
       throws Exception {
     configurePathExpressions(project, PathExpressions.SIMPLE.name());
-    assertThat(cfgSnapshot().getPathExpressions("master"))
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
         .value()
         .isEqualTo(PathExpressions.SIMPLE);
   }
@@ -1084,14 +1088,16 @@
   @Test
   public void pathExpressionsAreInheritedFromParentProject() throws Exception {
     configurePathExpressions(allProjects, PathExpressions.GLOB.name());
-    assertThat(cfgSnapshot().getPathExpressions("master")).value().isEqualTo(PathExpressions.GLOB);
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
+        .value()
+        .isEqualTo(PathExpressions.GLOB);
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.pathExpressions", value = "GLOB")
   public void inheritedPathExpressionsOverrideDefaultPathExpressions() throws Exception {
     configurePathExpressions(allProjects, PathExpressions.SIMPLE.name());
-    assertThat(cfgSnapshot().getPathExpressions("master"))
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
         .value()
         .isEqualTo(PathExpressions.SIMPLE);
   }
@@ -1100,7 +1106,7 @@
   public void projectLevelPathExpressionsOverrideInheritedPathExpressions() throws Exception {
     configurePathExpressions(allProjects, PathExpressions.GLOB.name());
     configurePathExpressions(project, PathExpressions.SIMPLE.name());
-    assertThat(cfgSnapshot().getPathExpressions("master"))
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
         .value()
         .isEqualTo(PathExpressions.SIMPLE);
   }
@@ -1111,26 +1117,32 @@
       pathExpressionsAreReadFromGlobalConfigIfNonExistingPathExpressionsAreConfiguredOnProjectLevel()
           throws Exception {
     configurePathExpressions(project, "non-existing-path-expressions");
-    assertThat(cfgSnapshot().getPathExpressions("master")).value().isEqualTo(PathExpressions.GLOB);
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
+        .value()
+        .isEqualTo(PathExpressions.GLOB);
   }
 
   @Test
   public void projectLevelPathExpressionsForOtherProjectHasNoEffect() throws Exception {
     Project.NameKey otherProject = projectOperations.newProject().create();
     configurePathExpressions(otherProject, PathExpressions.GLOB.name());
-    assertThat(cfgSnapshot().getPathExpressions("master")).isEmpty();
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master")).isEmpty();
   }
 
   @Test
   public void getPathExpressionsConfiguredOnBranchLevel() throws Exception {
     configurePathExpressions(project, "refs/heads/master", PathExpressions.GLOB.name());
-    assertThat(cfgSnapshot().getPathExpressions("master")).value().isEqualTo(PathExpressions.GLOB);
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
+        .value()
+        .isEqualTo(PathExpressions.GLOB);
   }
 
   @Test
   public void getPathExpressionsConfiguredOnBranchLevelShortName() throws Exception {
     configurePathExpressions(project, "master", PathExpressions.GLOB.name());
-    assertThat(cfgSnapshot().getPathExpressions("master")).value().isEqualTo(PathExpressions.GLOB);
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
+        .value()
+        .isEqualTo(PathExpressions.GLOB);
   }
 
   @Test
@@ -1139,7 +1151,7 @@
           throws Exception {
     configurePathExpressions(project, "master", PathExpressions.GLOB.name());
     configurePathExpressions(project, "refs/heads/master", PathExpressions.SIMPLE.name());
-    assertThat(cfgSnapshot().getPathExpressions("master"))
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
         .value()
         .isEqualTo(PathExpressions.SIMPLE);
   }
@@ -1148,7 +1160,7 @@
   public void branchLevelPathExpressionsOverridesProjectLevelPathExpressions() throws Exception {
     configurePathExpressions(project, PathExpressions.GLOB.name());
     configurePathExpressions(project, "master", PathExpressions.SIMPLE.name());
-    assertThat(cfgSnapshot().getPathExpressions("master"))
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
         .value()
         .isEqualTo(PathExpressions.SIMPLE);
   }
@@ -1171,13 +1183,15 @@
               BackendConfig.KEY_PATH_EXPRESSIONS,
               "non-existing-path-expressions");
         });
-    assertThat(cfgSnapshot().getPathExpressions("master")).value().isEqualTo(PathExpressions.GLOB);
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master"))
+        .value()
+        .isEqualTo(PathExpressions.GLOB);
   }
 
   @Test
   public void branchLevelPathExpressionsForOtherBranchHaveNoEffect() throws Exception {
     configurePathExpressions(project, "foo", PathExpressions.GLOB.name());
-    assertThat(cfgSnapshot().getPathExpressions("master")).isEmpty();
+    OptionalSubject.assertThat(cfgSnapshot().getPathExpressions("master")).isEmpty();
   }
 
   @Test
diff --git a/javatests/com/google/gerrit/plugins/codeowners/backend/config/GeneralConfigTest.java b/javatests/com/google/gerrit/plugins/codeowners/backend/config/GeneralConfigTest.java
index 17663b2..819411a 100644
--- a/javatests/com/google/gerrit/plugins/codeowners/backend/config/GeneralConfigTest.java
+++ b/javatests/com/google/gerrit/plugins/codeowners/backend/config/GeneralConfigTest.java
@@ -39,7 +39,6 @@
 import static com.google.gerrit.plugins.codeowners.backend.config.GeneralConfig.KEY_REJECT_NON_RESOLVABLE_IMPORTS;
 import static com.google.gerrit.plugins.codeowners.backend.config.GeneralConfig.SECTION_VALIDATION;
 import static com.google.gerrit.testing.GerritJUnit.assertThrows;
-import static com.google.gerrit.truth.OptionalSubject.assertThat;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
@@ -54,6 +53,7 @@
 import com.google.gerrit.server.git.validators.CommitValidationMessage;
 import com.google.gerrit.server.git.validators.ValidationMessage;
 import com.google.gerrit.testing.ConfigSuite;
+import com.google.gerrit.truth.OptionalSubject;
 import org.eclipse.jgit.lib.Config;
 import org.junit.Before;
 import org.junit.Test;
@@ -84,14 +84,16 @@
 
   @Test
   public void noFileExtensionConfigured() throws Exception {
-    assertThat(generalConfig.getFileExtension(new Config())).isEmpty();
+    OptionalSubject.assertThat(generalConfig.getFileExtension(new Config())).isEmpty();
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.fileExtension", value = "foo")
   public void fileExtensionIsRetrievedFromGerritConfigIfNotSpecifiedOnProjectLevel()
       throws Exception {
-    assertThat(generalConfig.getFileExtension(new Config())).value().isEqualTo("foo");
+    OptionalSubject.assertThat(generalConfig.getFileExtension(new Config()))
+        .value()
+        .isEqualTo("foo");
   }
 
   @Test
@@ -99,7 +101,7 @@
   public void fileExtensionInPluginConfigOverridesFileExtensionInGerritConfig() throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_CODE_OWNERS, /* subsection= */ null, KEY_FILE_EXTENSION, "bar");
-    assertThat(generalConfig.getFileExtension(cfg)).value().isEqualTo("bar");
+    OptionalSubject.assertThat(generalConfig.getFileExtension(cfg)).value().isEqualTo("bar");
   }
 
   @Test
@@ -401,7 +403,7 @@
 
   @Test
   public void noBranchSpecificRejectNonResolvableCodeOwnersConfiguration() throws Exception {
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), new Config()))
         .isEmpty();
@@ -416,7 +418,7 @@
         "refs/heads/foo",
         KEY_REJECT_NON_RESOLVABLE_CODE_OWNERS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -431,7 +433,7 @@
         "refs/heads/foo/*",
         KEY_REJECT_NON_RESOLVABLE_CODE_OWNERS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -446,7 +448,7 @@
         "^refs/heads/.*foo.*",
         KEY_REJECT_NON_RESOLVABLE_CODE_OWNERS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -461,7 +463,7 @@
         "^refs/heads/[",
         KEY_REJECT_NON_RESOLVABLE_CODE_OWNERS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -476,7 +478,7 @@
         "refs/heads/master",
         KEY_REJECT_NON_RESOLVABLE_CODE_OWNERS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -492,7 +494,7 @@
         "refs/heads/*",
         KEY_REJECT_NON_RESOLVABLE_CODE_OWNERS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -508,7 +510,7 @@
         "^refs/heads/.*bar.*",
         KEY_REJECT_NON_RESOLVABLE_CODE_OWNERS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "foobarbaz"), cfg))
         .value()
@@ -521,7 +523,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/master", KEY_REJECT_NON_RESOLVABLE_CODE_OWNERS, "INVALID");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -549,7 +551,7 @@
 
     // it is non-deterministic which of the branch-specific configurations takes precedence, but
     // since they all configure the same value it's not important for this assertion
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableCodeOwnersForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -638,7 +640,7 @@
 
   @Test
   public void noBranchSpecificRejectNonResolvableImportsConfiguration() throws Exception {
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), new Config()))
         .isEmpty();
@@ -653,7 +655,7 @@
         "refs/heads/foo",
         KEY_REJECT_NON_RESOLVABLE_IMPORTS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -668,7 +670,7 @@
         "refs/heads/foo/*",
         KEY_REJECT_NON_RESOLVABLE_IMPORTS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -683,7 +685,7 @@
         "^refs/heads/.*foo.*",
         KEY_REJECT_NON_RESOLVABLE_IMPORTS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -695,7 +697,7 @@
     Config cfg = new Config();
     cfg.setBoolean(
         SECTION_VALIDATION, "^refs/heads/[", KEY_REJECT_NON_RESOLVABLE_IMPORTS, /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -710,7 +712,7 @@
         "refs/heads/master",
         KEY_REJECT_NON_RESOLVABLE_IMPORTS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -723,7 +725,7 @@
     Config cfg = new Config();
     cfg.setBoolean(
         SECTION_VALIDATION, "refs/heads/*", KEY_REJECT_NON_RESOLVABLE_IMPORTS, /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -739,7 +741,7 @@
         "^refs/heads/.*bar.*",
         KEY_REJECT_NON_RESOLVABLE_IMPORTS,
         /* value= */ false);
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "foobarbaz"), cfg))
         .value()
@@ -752,7 +754,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/master", KEY_REJECT_NON_RESOLVABLE_IMPORTS, "INVALID");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -777,7 +779,7 @@
 
     // it is non-deterministic which of the branch-specific configurations takes precedence, but
     // since they all configure the same value it's not important for this assertion
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getRejectNonResolvableImportsForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -889,7 +891,7 @@
 
   @Test
   public void noBranchSpecificEnableValidationOnBranchCreationConfiguration() throws Exception {
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), new Config()))
         .isEmpty();
@@ -901,7 +903,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/foo", KEY_ENABLE_VALIDATION_ON_BRANCH_CREATION, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -913,7 +915,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/foo/*", KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -928,7 +930,7 @@
         "^refs/heads/.*foo.*",
         KEY_ENABLE_VALIDATION_ON_BRANCH_CREATION,
         "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -940,7 +942,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "^refs/heads/[", KEY_ENABLE_VALIDATION_ON_BRANCH_CREATION, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -952,7 +954,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/master", KEY_ENABLE_VALIDATION_ON_BRANCH_CREATION, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -965,7 +967,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/*", KEY_ENABLE_VALIDATION_ON_BRANCH_CREATION, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -981,7 +983,7 @@
         "^refs/heads/.*bar.*",
         KEY_ENABLE_VALIDATION_ON_BRANCH_CREATION,
         "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "foobarbaz"), cfg))
         .value()
@@ -997,7 +999,7 @@
         "refs/heads/master",
         KEY_ENABLE_VALIDATION_ON_BRANCH_CREATION,
         "INVALID");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1016,7 +1018,7 @@
 
     // it is non-deterministic which of the branch-specific configurations takes precedence, but
     // since they all configure the same value it's not important for this assertion
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForBranchCreationForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -1117,7 +1119,7 @@
 
   @Test
   public void noBranchSpecificEnableValidationOnCommitReceivedConfiguration() throws Exception {
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), new Config()))
         .isEmpty();
@@ -1129,7 +1131,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/foo", KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1141,7 +1143,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/foo/*", KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1156,7 +1158,7 @@
         "^refs/heads/.*foo.*",
         KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED,
         "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1168,7 +1170,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "^refs/heads/[", KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1180,7 +1182,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/master", KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -1193,7 +1195,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/*", KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -1209,7 +1211,7 @@
         "^refs/heads/.*bar.*",
         KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED,
         "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "foobarbaz"), cfg))
         .value()
@@ -1225,7 +1227,7 @@
         "refs/heads/master",
         KEY_ENABLE_VALIDATION_ON_COMMIT_RECEIVED,
         "INVALID");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1244,7 +1246,7 @@
 
     // it is non-deterministic which of the branch-specific configurations takes precedence, but
     // since they all configure the same value it's not important for this assertion
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -1343,7 +1345,7 @@
 
   @Test
   public void noBranchSpecificEnableValidationOnSubmitConfiguration() throws Exception {
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "master"), new Config()))
         .isEmpty();
@@ -1354,7 +1356,7 @@
       throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_VALIDATION, "refs/heads/foo", KEY_ENABLE_VALIDATION_ON_SUBMIT, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1365,7 +1367,7 @@
       throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_VALIDATION, "refs/heads/foo/*", KEY_ENABLE_VALIDATION_ON_SUBMIT, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1377,7 +1379,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "^refs/heads/.*foo.*", KEY_ENABLE_VALIDATION_ON_SUBMIT, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForCommitReceivedForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1388,7 +1390,7 @@
       throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_VALIDATION, "^refs/heads/[", KEY_ENABLE_VALIDATION_ON_SUBMIT, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1399,7 +1401,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/master", KEY_ENABLE_VALIDATION_ON_SUBMIT, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -1411,7 +1413,7 @@
       throws Exception {
     Config cfg = new Config();
     cfg.setString(SECTION_VALIDATION, "refs/heads/*", KEY_ENABLE_VALIDATION_ON_SUBMIT, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -1423,7 +1425,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "^refs/heads/.*bar.*", KEY_ENABLE_VALIDATION_ON_SUBMIT, "false");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "foobarbaz"), cfg))
         .value()
@@ -1436,7 +1438,7 @@
     Config cfg = new Config();
     cfg.setString(
         SECTION_VALIDATION, "refs/heads/master", KEY_ENABLE_VALIDATION_ON_SUBMIT, "INVALID");
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .isEmpty();
@@ -1453,7 +1455,7 @@
 
     // it is non-deterministic which of the branch-specific configurations takes precedence, but
     // since they all configure the same value it's not important for this assertion
-    assertThat(
+    OptionalSubject.assertThat(
             generalConfig.getCodeOwnerConfigValidationPolicyForSubmitForBranch(
                 BranchNameKey.create(project, "master"), cfg))
         .value()
@@ -1856,14 +1858,14 @@
 
   @Test
   public void noOverrideInfoUrlConfigured() throws Exception {
-    assertThat(generalConfig.getOverrideInfoUrl(new Config())).isEmpty();
+    OptionalSubject.assertThat(generalConfig.getOverrideInfoUrl(new Config())).isEmpty();
   }
 
   @Test
   @GerritConfig(name = "plugin.code-owners.overrideInfoUrl", value = "http://foo.example.com")
   public void overrideInfoIsRetrievedFromGerritConfigIfNotSpecifiedOnProjectLevel()
       throws Exception {
-    assertThat(generalConfig.getOverrideInfoUrl(new Config()))
+    OptionalSubject.assertThat(generalConfig.getOverrideInfoUrl(new Config()))
         .value()
         .isEqualTo("http://foo.example.com");
   }
@@ -1878,7 +1880,9 @@
         /* subsection= */ null,
         KEY_OVERRIDE_INFO_URL,
         "http://bar.example.com");
-    assertThat(generalConfig.getOverrideInfoUrl(cfg)).value().isEqualTo("http://bar.example.com");
+    OptionalSubject.assertThat(generalConfig.getOverrideInfoUrl(cfg))
+        .value()
+        .isEqualTo("http://bar.example.com");
   }
 
   @Test
@@ -1892,7 +1896,8 @@
 
   @Test
   public void noInvalidCodeOwnerConfigInfoUrlConfigured() throws Exception {
-    assertThat(generalConfig.getInvalidCodeOwnerConfigInfoUrl(new Config())).isEmpty();
+    OptionalSubject.assertThat(generalConfig.getInvalidCodeOwnerConfigInfoUrl(new Config()))
+        .isEmpty();
   }
 
   @Test
@@ -1901,7 +1906,7 @@
       value = "http://foo.example.com")
   public void invalidCodeOwnerConfigInfoIsRetrievedFromGerritConfigIfNotSpecifiedOnProjectLevel()
       throws Exception {
-    assertThat(generalConfig.getInvalidCodeOwnerConfigInfoUrl(new Config()))
+    OptionalSubject.assertThat(generalConfig.getInvalidCodeOwnerConfigInfoUrl(new Config()))
         .value()
         .isEqualTo("http://foo.example.com");
   }
@@ -1918,7 +1923,7 @@
         /* subsection= */ null,
         KEY_INVALID_CODE_OWNER_CONFIG_INFO_URL,
         "http://bar.example.com");
-    assertThat(generalConfig.getInvalidCodeOwnerConfigInfoUrl(cfg))
+    OptionalSubject.assertThat(generalConfig.getInvalidCodeOwnerConfigInfoUrl(cfg))
         .value()
         .isEqualTo("http://bar.example.com");
   }