### Question:
ChangeTelnetHandler implements TelnetHandler { @Override public String telnet(Channel channel, String message) { if (message == null || message.length() == 0) { return "Please input service name, eg: \r\ncd XxxService\r\ncd com.xxx.XxxService"; } StringBuilder buf = new StringBuilder(); if (message.equals("/") || message.equals("..")) { String service = (String) channel.getAttribute(SERVICE_KEY); channel.removeAttribute(SERVICE_KEY); buf.append("Cancelled default service " + service + "."); } else { boolean found = false; for (Exporter<?> exporter : DubboProtocol.getDubboProtocol().getExporters()) { if (message.equals(exporter.getInvoker().getInterface().getSimpleName()) || message.equals(exporter.getInvoker().getInterface().getName()) || message.equals(exporter.getInvoker().getUrl().getPath())) { found = true; break; } } if (found) { channel.setAttribute(SERVICE_KEY, message); buf.append("Used the " + message + " as default.\r\nYou can cancel default service by command: cd /"); } else { buf.append("No such service " + message); } } return buf.toString(); }  @Override String telnet(Channel channel, String message); static final String SERVICE_KEY; }### Answer:
@Test public void testChangeName() throws RemotingException { DubboProtocol.getDubboProtocol().export(mockInvoker); String result = change.telnet(mockChannel, "org.apache.dubbo.rpc.protocol.dubbo.support.DemoService"); assertEquals("Used the org.apache.dubbo.rpc.protocol.dubbo.support.DemoService as default.\r\nYou can cancel default service by command: cd /", result); }
@Test public void testChangeCancel() throws RemotingException { String result = change.telnet(mockChannel, ".."); assertEquals("Cancelled default service org.apache.dubbo.rpc.protocol.dubbo.support.DemoService.", result); }
@Test public void testChangeCancel2() throws RemotingException { String result = change.telnet(mockChannel, "/"); assertEquals("Cancelled default service org.apache.dubbo.rpc.protocol.dubbo.support.DemoService.", result); }