all: Prefer mock+delegatesTo() over Mockito.spy()

Spies are really magical and easily produce unexpected results. Using them in
tests can easily yield tests that don't do what you think they do. Delegation
is much safer when possible.

Delegation doesn't work when methods `return true`, final methods, and with
restricted visibility, though. So CensusModulesTest and
MaxConnectionIdleManagerTest are left as-is.

3 files changed, 11 insertions, 7 deletions

diff --git a/examples/src/test/java/io/grpc/examples/header/HeaderClientInterceptorTest.java b/examples/src/test/java/io/grpc/examples/header/HeaderClientInterceptorTest.java
index b5e286955..0123ce961 100644
--- a/examples/src/test/java/io/grpc/examples/header/HeaderClientInterceptorTest.java
+++ b/examples/src/test/java/io/grpc/examples/header/HeaderClientInterceptorTest.java
@@ -18,7 +18,8 @@ package io.grpc.examples.header;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
-import static org.mockito.Mockito.spy;
+import static org.mockito.AdditionalAnswers.delegatesTo;
+import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 
 import io.grpc.ClientInterceptors;
@@ -59,14 +60,14 @@ public class HeaderClientInterceptorTest {
   @Rule
   public final GrpcServerRule grpcServerRule = new GrpcServerRule().directExecutor();
 
-  private final ServerInterceptor mockServerInterceptor = spy(
+  private final ServerInterceptor mockServerInterceptor = mock(ServerInterceptor.class, delegatesTo(
       new ServerInterceptor() {
         @Override
         public <ReqT, RespT> Listener<ReqT> interceptCall(
             ServerCall<ReqT, RespT> call, Metadata headers, ServerCallHandler<ReqT, RespT> next) {
           return next.startCall(call, headers);
         }
-      });
+      }));
 
   @Test
   public void clientHeaderDeliveredToServer() {
diff --git a/examples/src/test/java/io/grpc/examples/header/HeaderServerInterceptorTest.java b/examples/src/test/java/io/grpc/examples/header/HeaderServerInterceptorTest.java
index bbf222a10..64617de36 100644
--- a/examples/src/test/java/io/grpc/examples/header/HeaderServerInterceptorTest.java
+++ b/examples/src/test/java/io/grpc/examples/header/HeaderServerInterceptorTest.java
@@ -18,7 +18,8 @@ package io.grpc.examples.header;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
-import static org.mockito.Mockito.spy;
+import static org.mockito.AdditionalAnswers.delegatesTo;
+import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 
 import io.grpc.CallOptions;
@@ -87,7 +88,7 @@ public class HeaderServerInterceptorTest {
           @Override
           public void start(Listener<RespT> responseListener, Metadata headers) {
             spyListener = responseListener =
-                spy(new SimpleForwardingClientCallListener(responseListener) {});
+                mock(ClientCall.Listener.class, delegatesTo(responseListener));
             super.start(responseListener, headers);
           }
         };
diff --git a/examples/src/test/java/io/grpc/examples/helloworld/HelloWorldClientTest.java b/examples/src/test/java/io/grpc/examples/helloworld/HelloWorldClientTest.java
index b44b6f0e1..7d1237de5 100644
--- a/examples/src/test/java/io/grpc/examples/helloworld/HelloWorldClientTest.java
+++ b/examples/src/test/java/io/grpc/examples/helloworld/HelloWorldClientTest.java
@@ -17,7 +17,8 @@
 package io.grpc.examples.helloworld;
 
 import static org.junit.Assert.assertEquals;
-import static org.mockito.Mockito.spy;
+import static org.mockito.AdditionalAnswers.delegatesTo;
+import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 
 import io.grpc.stub.StreamObserver;
@@ -47,7 +48,8 @@ public class HelloWorldClientTest {
   @Rule
   public final GrpcServerRule grpcServerRule = new GrpcServerRule().directExecutor();
 
-  private final GreeterGrpc.GreeterImplBase serviceImpl = spy(new GreeterGrpc.GreeterImplBase() {});
+  private final GreeterGrpc.GreeterImplBase serviceImpl =
+      mock(GreeterGrpc.GreeterImplBase.class, delegatesTo(new GreeterGrpc.GreeterImplBase() {}));
   private HelloWorldClient client;
 
   @Before