diff --git a/benchmark/src/main/java/org/capnproto/benchmark/TestCase.java b/benchmark/src/main/java/org/capnproto/benchmark/TestCase.java
index 7800c6c..0d9faf6 100644
--- a/benchmark/src/main/java/org/capnproto/benchmark/TestCase.java
+++ b/benchmark/src/main/java/org/capnproto/benchmark/TestCase.java
@@ -13,14 +13,9 @@ public abstract class TestCase<RequestFactory extends StructFactory<RequestBuild
     public abstract void handleRequest(RequestReader request, ResponseBuilder response);
     public abstract boolean checkResponse(ResponseReader response, Expectation expected);
 
-    public void execute(String[] args, RequestFactory requestFactory, ResponseFactory responseFactory) {
 
-        if (args.length != 4) {
-            System.out.println("USAGE: TestCase MODE REUSE COMPRESSION ITERATION_COUNT");
-            return;
-        }
-
-        long iters = Long.parseLong(args[3]);
+    public void passByObject(RequestFactory requestFactory, ResponseFactory responseFactory,
+                             long iters) {
 
         Common.FastRand rng = new Common.FastRand();
 
@@ -35,7 +30,40 @@ public abstract class TestCase<RequestFactory extends StructFactory<RequestBuild
                 System.out.println("mismatch!");
             }
         }
+    }
+
+    public void passByBytes(RequestFactory requestFactory, ResponseFactory responseFactory,
+                            long iters) {
+
+        Common.FastRand rng = new Common.FastRand();
+
+        for (int i = 0; i < iters; ++i) {
+            MessageBuilder requestMessage = new MessageBuilder();
+            MessageBuilder responseMessage = new MessageBuilder();
+            // TODO
+            throw new Error("unimplemented");
+        }
+    }
 
 
+    public void execute(String[] args, RequestFactory requestFactory, ResponseFactory responseFactory) {
+
+        if (args.length != 4) {
+            System.out.println("USAGE: TestCase MODE REUSE COMPRESSION ITERATION_COUNT");
+            return;
+        }
+
+        String mode = args[0];
+        String reuse = args[1];
+        String compression = args[2];
+        long iters = Long.parseLong(args[3]);
+
+        if (mode.equals("object")) {
+            passByObject(requestFactory, responseFactory, iters);
+        } else if (mode.equals("bytes")) {
+            passByBytes(requestFactory, responseFactory, iters);
+        } else {
+            System.out.println("unknown mode: " + mode);
+        }
     }
 }