diff --git a/lib/modules/only_for_test.go b/lib/modules/only_for_test.go
new file mode 100644
index 0000000..8f3143a
--- /dev/null
+++ b/lib/modules/only_for_test.go
@@ -0,0 +1,8 @@
+package modules
+
+import "io"
+
+// NewRW exposes newRW for unit tests.
+func NewRW() io.ReadWriteCloser {
+	return newRW()
+}
diff --git a/lib/modules/queue_rw.go b/lib/modules/queue_rw.go
index 8dbba9f..b4c83e9 100644
--- a/lib/modules/queue_rw.go
+++ b/lib/modules/queue_rw.go
@@ -8,8 +8,6 @@
 	"veyron.io/veyron/veyron/runtimes/google/lib/upcqueue"
 )
 
-// TODO(caprita): Write unit tests.
-
 // queueRW implements a ReadWriteCloser backed by an unbounded in-memory
 // producer-consumer queue.
 type queueRW struct {
@@ -47,6 +45,7 @@
 		q.buf, q.buffered = b, len(b)
 	}
 	copied := copy(p, q.buf[:q.buffered])
+	q.buf = q.buf[copied:]
 	q.buffered -= copied
 	return copied, nil
 }
diff --git a/lib/modules/queue_rw_test.go b/lib/modules/queue_rw_test.go
new file mode 100644
index 0000000..735c301
--- /dev/null
+++ b/lib/modules/queue_rw_test.go
@@ -0,0 +1,60 @@
+package modules_test
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"veyron.io/veyron/veyron/lib/modules"
+	"veyron.io/veyron/veyron/lib/testutil"
+)
+
+func init() {
+	if !modules.IsModulesProcess() {
+		testutil.Init()
+	}
+}
+func TestQueueRW(t *testing.T) {
+	q := modules.NewRW()
+	size := testutil.Rand.Intn(1000)
+	data := testutil.RandomBytes(size)
+	begin := 0
+	for {
+		end := begin + testutil.Rand.Intn(100) + 1
+		if end > len(data) {
+			end = len(data)
+		}
+		n, err := q.Write(data[begin:end])
+		if err != nil {
+			t.Fatalf("Write failed: %v", err)
+		}
+		begin = begin + n
+		if begin == len(data) {
+			break
+		}
+	}
+	// This marks EOF.
+	if _, err := q.Write([]byte{}); err != nil {
+		t.Fatalf("err %v", err)
+	}
+	readData := make([]byte, 0, size)
+	for {
+		buf := make([]byte, testutil.Rand.Intn(100)+1)
+		n, err := q.Read(buf)
+		if n > 0 {
+			readData = append(readData, buf[:n]...)
+		}
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			t.Fatalf("Read failed: %v", err)
+		}
+	}
+	if size != len(readData) {
+		t.Fatalf("Mismatching data size: %d != %d", size, len(readData))
+	}
+	if !bytes.Equal(data, readData) {
+		t.Fatalf("Diffing data:\n%v\n%v", data, readData)
+	}
+}