Add zero length test

basic/tcp-client-server/src/test/java/org/springframework/integration/samples/tcpclientserver/TcpClientServerDemoTest.java

@@ -48,6 +48,13 @@ public class TcpClientServerDemoTest {
 		assertEquals("echo:Hello world!", result);
 	}
 	
+	@Test
+	public void testZeroLength() {
+		String result = gw.send("");
+		System.out.println(result);
+		assertEquals("echo:", result);
+	}
+
 	@Test
 	public void testFail() {
 		String result = gw.send("FAIL");