code: @Given("^I save the IP of an unused node in hosts '(.+?)' in the in environment variable '(.+?)'?$")
      public void getUnusedNode(String hosts, String envVar) throws Exception {
          Set<String> hostList = new HashSet(Arrays.asList(hosts.split(",")));
  
          //Get the list of currently used hosts
          commonspec.executeCommand("dcos task | awk '{print $2}'", 0, null);
          String results = commonspec.getRemoteSSHConnection().getResult();
          Set<String> usedHosts = new HashSet(Arrays.asList(results.replaceAll("\r", "").split("\n")));
  
          //We get the nodes not being used
          hostList.removeAll(usedHosts);
  
          if (hostList.size() == 0) {
              throw new IllegalStateException("No unused nodes in the cluster.");
          } else {
              //Pick the first available node
              ThreadProperty.set(envVar, hostList.iterator().next());
          }
      }
docs: Checks if there are any unused nodes in the cluster and returns the IP of one of them.
  REQUIRES A PREVIOUSLY-ESTABLISHED SSH CONNECTION TO DCOS-CLI TO WORK
  
  @param hosts:  list of IPs that will be investigated
  @param envVar: environment variable name
  @throws Exception