diff --git a/SECURITY.md b/SECURITY.md
index c330208395..5a7e2f5115 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -65,7 +65,7 @@ with OpenSSL](#tls-with-netty-tcnative-on-openssl) are other valid options.
 [Apache Tomcat's tcnative](http://tomcat.apache.org/native-doc/) and is a JNI
 wrapper around OpenSSL/BoringSSL/LibreSSL.
 
-We recommend BoringSSL for its simplicitly and low occurence of security
+We recommend BoringSSL for its simplicitly and low occurrence of security
 vulnerabilities relative to OpenSSL. BoringSSL is used by Conscrypt as well.
 
 ### TLS with netty-tcnative on BoringSSL
diff --git a/context/src/test/java/io/grpc/ThreadLocalContextStorageTest.java b/context/src/test/java/io/grpc/ThreadLocalContextStorageTest.java
index 3ab4ed49cc..5e3f7ea26a 100644
--- a/context/src/test/java/io/grpc/ThreadLocalContextStorageTest.java
+++ b/context/src/test/java/io/grpc/ThreadLocalContextStorageTest.java
@@ -25,7 +25,7 @@ import org.junit.runners.JUnit4;
 @RunWith(JUnit4.class)
 public final class ThreadLocalContextStorageTest {
   private static final Context.Key<Object> KEY = Context.key("test-key");
-  private ThreadLocalContextStorage storage = new ThreadLocalContextStorage();
+  private final ThreadLocalContextStorage storage = new ThreadLocalContextStorage();
 
   @Test
   public void detach_threadLocalClearedOnRoot() {
diff --git a/core/src/test/java/io/grpc/inprocess/InProcessTransportTest.java b/core/src/test/java/io/grpc/inprocess/InProcessTransportTest.java
index 829e0404b4..cd89f2b258 100644
--- a/core/src/test/java/io/grpc/inprocess/InProcessTransportTest.java
+++ b/core/src/test/java/io/grpc/inprocess/InProcessTransportTest.java
@@ -16,12 +16,12 @@
 
 package io.grpc.inprocess;
 
+import com.google.common.collect.ImmutableList;
 import io.grpc.ServerStreamTracer;
 import io.grpc.internal.GrpcUtil;
 import io.grpc.internal.InternalServer;
 import io.grpc.internal.ManagedClientTransport;
 import io.grpc.internal.testing.AbstractTransportTest;
-import java.util.Collections;
 import java.util.List;
 import org.junit.Ignore;
 import org.junit.Test;
@@ -41,7 +41,7 @@ public class InProcessTransportTest extends AbstractTransportTest {
     InProcessServerBuilder builder = InProcessServerBuilder
         .forName(TRANSPORT_NAME)
         .maxInboundMetadataSize(GrpcUtil.DEFAULT_MAX_HEADER_LIST_SIZE);
-    return Collections.singletonList(new InProcessServer(builder, streamTracerFactories));
+    return ImmutableList.of(new InProcessServer(builder, streamTracerFactories));
   }
 
   @Override
diff --git a/netty/src/test/java/io/grpc/netty/NettyServerBuilderTest.java b/netty/src/test/java/io/grpc/netty/NettyServerBuilderTest.java
index 98ba27c837..cf5f1d6b59 100644
--- a/netty/src/test/java/io/grpc/netty/NettyServerBuilderTest.java
+++ b/netty/src/test/java/io/grpc/netty/NettyServerBuilderTest.java
@@ -19,10 +19,10 @@ package io.grpc.netty;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.truth.Truth;
 import io.grpc.ServerStreamTracer.Factory;
 import io.netty.handler.ssl.SslContext;
-import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 import org.junit.Rule;
@@ -31,7 +31,6 @@ import org.junit.rules.ExpectedException;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
 
-
 /**
  * Unit tests for {@link NettyServerBuilder}.
  */
@@ -45,7 +44,7 @@ public class NettyServerBuilderTest {
   @Test
   public void createMultipleServers() {
     builder.addPort(8081);
-    List<NettyServer> servers = builder.buildTransportServers(Collections.<Factory>emptyList());
+    List<NettyServer> servers = builder.buildTransportServers(ImmutableList.<Factory>of());
 
     Truth.assertThat(servers).hasSize(2);
   }