feat: add some test case

remoting/src/test/java/org/apache/rocketmq/remoting/netty/NettyClientConfigTest.java

+package org.apache.rocketmq.remoting.netty;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.junit.MockitoJUnitRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@RunWith(MockitoJUnitRunner.class)
+public class NettyClientConfigTest {
+
+  @Test
+  public void testChangeConfigBySystemProperty() throws NoSuchFieldException, IllegalAccessException {
+
+    System.setProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_CLIENT_WORKER_SIZE, "1");
+    System.setProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_CLIENT_ONEWAY_SEMAPHORE_VALUE, "1023");
+    System.setProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_CLIENT_ASYNC_SEMAPHORE_VALUE, "1024");
+    System.setProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_CLIENT_CONNECT_TIMEOUT, "2000");
+    System.setProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_CLIENT_CHANNEL_MAX_IDLE_SECONDS, "60");
+    System.setProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_SOCKET_SNDBUF_SIZE, "16383");
+    System.setProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_SOCKET_RCVBUF_SIZE, "16384");
+    System.setProperty(NettySystemConfig.COM_ROCKETMQ_REMOTING_CLIENT_CLOSE_SOCKET_IF_TIMEOUT, "false");
+
+    NettyClientConfig changedConfig = new NettyClientConfig();
+    assertThat(changedConfig.getClientWorkerThreads()).isEqualTo(1);
+    assertThat(changedConfig.getClientOnewaySemaphoreValue()).isEqualTo(1023);
+    assertThat(changedConfig.getClientAsyncSemaphoreValue()).isEqualTo(1024);
+    assertThat(changedConfig.getConnectTimeoutMillis()).isEqualTo(2000);
+    assertThat(changedConfig.getClientChannelMaxIdleTimeSeconds()).isEqualTo(60);
+    assertThat(changedConfig.getClientSocketSndBufSize()).isEqualTo(16383);
+    assertThat(changedConfig.getClientSocketRcvBufSize()).isEqualTo(16384);
+    assertThat(changedConfig.isClientCloseSocketIfTimeout()).isEqualTo(false);
+  }
+}