diff --git a/src/main/java/com/googlesource/gerrit/plugins/multisite/cache/CachePatternMatcher.java b/src/main/java/com/googlesource/gerrit/plugins/multisite/cache/CachePatternMatcher.java
index b8521a3..2dcb09a 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/multisite/cache/CachePatternMatcher.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/multisite/cache/CachePatternMatcher.java
@@ -25,7 +25,7 @@
 
 @Singleton
 class CachePatternMatcher {
-  private static final List<String> DEFAULT_PATTERNS =
+  private static final ImmutableList<String> DEFAULT_PATTERNS =
       ImmutableList.of("^groups.*", "ldap_groups", "ldap_usernames", "projects", "sshkeys");
 
   private final Pattern pattern;
diff --git a/src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexProjectHandler.java b/src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexProjectHandler.java
index ce6804e..6da9681 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexProjectHandler.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexProjectHandler.java
@@ -23,6 +23,7 @@
 import com.googlesource.gerrit.plugins.multisite.index.ForwardedIndexExecutor;
 import com.googlesource.gerrit.plugins.multisite.index.ProjectChecker;
 import java.util.Optional;
+import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
@@ -92,20 +93,22 @@
         projectName,
         retryInterval);
 
-    indexExecutor.schedule(
-        () -> {
-          Context.setForwardedEvent(true);
-          if (!attemptIndex(projectName, event)) {
-            log.warn(
-                "Attempt {} to index project {} failed, scheduling again after {} msecs",
-                retryCount,
-                projectName,
-                retryInterval);
-            rescheduleIndex(projectName, event, retryCount + 1);
-          }
-        },
-        retryInterval,
-        TimeUnit.MILLISECONDS);
+    @SuppressWarnings("unused")
+    Future<?> possiblyIgnoredError =
+        indexExecutor.schedule(
+            () -> {
+              Context.setForwardedEvent(true);
+              if (!attemptIndex(projectName, event)) {
+                log.warn(
+                    "Attempt {} to index project {} failed, scheduling again after {} msecs",
+                    retryCount,
+                    projectName,
+                    retryInterval);
+                rescheduleIndex(projectName, event, retryCount + 1);
+              }
+            },
+            retryInterval,
+            TimeUnit.MILLISECONDS);
   }
 
   @Override
diff --git a/src/main/java/com/googlesource/gerrit/plugins/multisite/validation/ProjectVersionRefUpdate.java b/src/main/java/com/googlesource/gerrit/plugins/multisite/validation/ProjectVersionRefUpdate.java
index 28eddbb..ea7dada 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/multisite/validation/ProjectVersionRefUpdate.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/multisite/validation/ProjectVersionRefUpdate.java
@@ -36,7 +36,6 @@
 import com.googlesource.gerrit.plugins.multisite.forwarder.Context;
 import java.io.IOException;
 import java.util.Optional;
-import java.util.Set;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectIdRef;
@@ -48,7 +47,7 @@
 @Singleton
 public class ProjectVersionRefUpdate implements EventListener {
   private static final FluentLogger logger = FluentLogger.forEnclosingClass();
-  private static final Set<RefUpdate.Result> SUCCESSFUL_RESULTS =
+  private static final ImmutableSet<RefUpdate.Result> SUCCESSFUL_RESULTS =
       ImmutableSet.of(RefUpdate.Result.NEW, RefUpdate.Result.FORCED, RefUpdate.Result.NO_CHANGE);
 
   public static final String MULTI_SITE_VERSIONING_REF = "refs/multi-site/version";
diff --git a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/BrokerForwarderTest.java b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/BrokerForwarderTest.java
index 5e2fc05..74d8917 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/BrokerForwarderTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/BrokerForwarderTest.java
@@ -67,7 +67,7 @@
     }
   }
 
-  public class TestEvent extends MultiSiteEvent {
+  public static class TestEvent extends MultiSiteEvent {
 
     protected TestEvent() {
       super("test");
diff --git a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedCacheEvictionHandlerTest.java b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedCacheEvictionHandlerTest.java
index 90ae8da..dbd358d 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedCacheEvictionHandlerTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedCacheEvictionHandlerTest.java
@@ -15,6 +15,7 @@
 package com.googlesource.gerrit.plugins.multisite.forwarder;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.testing.GerritJUnit.assertThrows;
 import static org.mockito.Mockito.doReturn;
 
 import com.google.common.cache.Cache;
@@ -48,10 +49,12 @@
   public void shouldThrowAnExceptionWhenCacheNotFound() throws Exception {
     CacheEntry entry = new CacheEntry("somePlugin", "unexistingCache", null);
 
-    exception.expect(CacheNotFoundException.class);
-    exception.expectMessage(
-        String.format("cache %s.%s not found", entry.getPluginName(), entry.getCacheName()));
-    handler.evict(entry);
+    CacheNotFoundException thrown =
+        assertThrows(CacheNotFoundException.class, () -> handler.evict(entry));
+    assertThat(thrown)
+        .hasMessageThat()
+        .isEqualTo(
+            String.format("cache %s.%s not found", entry.getPluginName(), entry.getCacheName()));
   }
 
   @Test
diff --git a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexAccountHandlerTest.java b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexAccountHandlerTest.java
index 32c6319..02efb77 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexAccountHandlerTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexAccountHandlerTest.java
@@ -61,9 +61,11 @@
 
   @Test
   public void deleteIsNotSupported() throws Exception {
-    exception.expect(UnsupportedOperationException.class);
-    exception.expectMessage("Delete from account index not supported");
-    handler.index(id, Operation.DELETE, Optional.empty());
+    UnsupportedOperationException thrown =
+        assertThrows(
+            UnsupportedOperationException.class,
+            () -> handler.index(id, Operation.DELETE, Optional.empty()));
+    assertThat(thrown).hasMessageThat().isEqualTo("Delete from account index not supported");
   }
 
   @Test
diff --git a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexChangeHandlerTest.java b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexChangeHandlerTest.java
index c52dfff..04d83c5 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexChangeHandlerTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexChangeHandlerTest.java
@@ -125,8 +125,9 @@
   @Test
   public void indexerThrowsStorageExceptionTryingToIndexChange() throws Exception {
     setupChangeAccessRelatedMocks(CHANGE_EXISTS, THROW_STORAGE_EXCEPTION, CHANGE_UP_TO_DATE);
-    exception.expect(StorageException.class);
-    handler.index(TEST_CHANGE_ID, Operation.INDEX, Optional.empty());
+    assertThrows(
+        StorageException.class,
+        () -> handler.index(TEST_CHANGE_ID, Operation.INDEX, Optional.empty()));
   }
 
   @Test
diff --git a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexGroupHandlerTest.java b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexGroupHandlerTest.java
index 2fe6e2e..c703512 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexGroupHandlerTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexGroupHandlerTest.java
@@ -61,9 +61,11 @@
 
   @Test
   public void deleteIsNotSupported() throws Exception {
-    exception.expect(UnsupportedOperationException.class);
-    exception.expectMessage("Delete from group index not supported");
-    handler.index(uuid, Operation.DELETE, Optional.empty());
+    UnsupportedOperationException thrown =
+        assertThrows(
+            UnsupportedOperationException.class,
+            () -> handler.index(uuid, Operation.DELETE, Optional.empty()));
+    assertThat(thrown).hasMessageThat().isEqualTo("Delete from group index not supported");
   }
 
   @Test
diff --git a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexProjectHandlerTest.java b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexProjectHandlerTest.java
index 1102cd2..9ed0f7d 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexProjectHandlerTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedIndexProjectHandlerTest.java
@@ -71,9 +71,11 @@
 
   @Test
   public void deleteIsNotSupported() throws Exception {
-    exception.expect(UnsupportedOperationException.class);
-    exception.expectMessage("Delete from project index not supported");
-    handler.index(nameKey, Operation.DELETE, Optional.empty());
+    UnsupportedOperationException thrown =
+        assertThrows(
+            UnsupportedOperationException.class,
+            () -> handler.index(nameKey, Operation.DELETE, Optional.empty()));
+    assertThat(thrown).hasMessageThat().isEqualTo("Delete from project index not supported");
   }
 
   @Test