code: protected MessageChannel resolveChannelName(String channelName, TestContext context) {
          if (endpointConfiguration.getChannelResolver() == null) {
              if (endpointConfiguration.getBeanFactory() != null) {
                  endpointConfiguration.setChannelResolver(new BeanFactoryChannelResolver(endpointConfiguration.getBeanFactory()));
              } else {
                  endpointConfiguration.setChannelResolver(new BeanFactoryChannelResolver(context.getApplicationContext()));
              }
          }
  
          return endpointConfiguration.getChannelResolver().resolveDestination(channelName);
      }
docs: Resolve the channel by name.
  @param channelName the name to resolve
  @param context
  @return the MessageChannel object