diff --git a/utils/nio/src/test/java/org/onlab/nio/TestMessage.java b/utils/nio/src/test/java/org/onlab/nio/TestMessage.java
new file mode 100644
index 0000000..00315ec
--- /dev/null
+++ b/utils/nio/src/test/java/org/onlab/nio/TestMessage.java
@@ -0,0 +1,39 @@
+package org.onlab.nio;
+
+/**
+ * Fixed-length message.
+ */
+public class TestMessage extends AbstractMessage {
+
+    private final byte[] data;
+
+    /**
+     * Creates a new message with the specified length.
+     *
+     * @param length message length
+     */
+    public TestMessage(int length) {
+        this.length = length;
+        data = new byte[length];
+    }
+
+    /**
+     * Creates a new message with the specified data.
+     *
+     * @param data message data
+     */
+    TestMessage(byte[] data) {
+        this.length = data.length;
+        this.data = data;
+    }
+
+    /**
+     * Gets the backing byte array data.
+     *
+     * @return backing byte array
+     */
+    public byte[] data() {
+        return data;
+    }
+
+}