@Test
  public void testStartGatewaySender_ErrorConditions() {
    Integer locator1Port = locatorSite1.getPort();

    // setup servers in Site #1
    server1 = clusterStartupRule.startServerVM(3, locator1Port);

    server1.invoke(() -> createSender("ln", 2, false, 100, 400, false, false, null, true));

    DistributedMember vm1Member = getMember(server1.getVM());
    String command = CliStrings.START_GATEWAYSENDER + " --" + CliStrings.START_GATEWAYSENDER__ID
        + "=ln --" + CliStrings.MEMBER + "=" + vm1Member.getId() + " --" + CliStrings.GROUP
        + "=SenserGroup1";
    gfsh.executeAndAssertThat(command).statusIsError()
        .containsOutput(CliStrings.PROVIDE_EITHER_MEMBER_OR_GROUP_MESSAGE);
  }
Test wan commands for error in input 1> start gateway-sender command needs only one of member
or group.
geode-wan/src/distributedTest/java/org/apache/geode/internal/cache/wan/wancommand/StartGatewaySenderCommandDUnitTest.java