diff --git a/benchmark/src/main/java/org/capnproto/benchmark/TestCase.java b/benchmark/src/main/java/org/capnproto/benchmark/TestCase.java
index 7fe9aac..394eb10 100644
--- a/benchmark/src/main/java/org/capnproto/benchmark/TestCase.java
+++ b/benchmark/src/main/java/org/capnproto/benchmark/TestCase.java
@@ -56,10 +56,24 @@ public abstract class TestCase<RequestFactory extends StructFactory<RequestBuild
                 org.capnproto.Serialize.writeMessage(writer, requestMessage);
             }
 
-            new org.capnproto.ArrayInputStream(requestBytes);
+            {
+                org.capnproto.MessageReader messageReader =
+                    org.capnproto.ByteChannelMessageReader.create(new org.capnproto.ArrayInputStream(requestBytes));
+                this.handleRequest(messageReader.getRoot(requestFactory), response);
+            }
 
-            // TODO
-            throw new Error("unimplemented");
+            {
+                org.capnproto.ArrayOutputStream writer = new org.capnproto.ArrayOutputStream(responseBytes);
+                org.capnproto.Serialize.writeMessage(writer, responseMessage);
+            }
+
+            {
+                org.capnproto.MessageReader messageReader =
+                    org.capnproto.ByteChannelMessageReader.create(new org.capnproto.ArrayInputStream(responseBytes));
+                if (!this.checkResponse(messageReader.getRoot(responseFactory), expected)) {
+                    throw new Error("incorrect response");
+                }
+            }
         }
     }
 
diff --git a/runtime/src/main/java/org/capnproto/ArrayInputStream.java b/runtime/src/main/java/org/capnproto/ArrayInputStream.java
index 1ac7c68..3195f34 100644
--- a/runtime/src/main/java/org/capnproto/ArrayInputStream.java
+++ b/runtime/src/main/java/org/capnproto/ArrayInputStream.java
@@ -9,7 +9,7 @@ public final class ArrayInputStream implements BufferedInputStream {
     public final ByteBuffer buf;
 
     public ArrayInputStream(ByteBuffer buf) {
-        this.buf = buf;
+        this.buf = buf.asReadOnlyBuffer();
     }
 
     public final int read(ByteBuffer dst) throws IOException {
diff --git a/runtime/src/main/java/org/capnproto/ArrayOutputStream.java b/runtime/src/main/java/org/capnproto/ArrayOutputStream.java
index a130212..92ff85d 100644
--- a/runtime/src/main/java/org/capnproto/ArrayOutputStream.java
+++ b/runtime/src/main/java/org/capnproto/ArrayOutputStream.java
@@ -9,7 +9,7 @@ public final class ArrayOutputStream implements BufferedOutputStream {
     public final ByteBuffer buf;
 
     public ArrayOutputStream(ByteBuffer buf) {
-        this.buf = buf;
+        this.buf = buf.duplicate();
     }
 
     public final int write(ByteBuffer src) throws IOException {