anchor.diff:        $discovery2->start();
         $discovery1->waitForUnit("etcd.service");
         $discovery2->waitForUnit("etcd.service");
  -      $discovery1->succeed("etcdctl set /foo/bar 'Hello world'");
  +      $discovery1->waitUntilSucceeds("etcdctl set /foo/bar 'Hello world'");
         $discovery2->waitUntilSucceeds("etcdctl get /foo/bar | grep 'Hello world'");
       };
     '';
  
positive.code:       $node2->start();
        $node1->waitForUnit("etcd.service");
        $node2->waitForUnit("etcd.service");
        $node1->succeed("etcdctl set /foo/bar 'Hello world'");
        $node2->waitUntilSucceeds("etcdctl get /foo/bar | grep 'Hello world'");
        $node1->shutdown();
        $node2->shutdown();
  
negative.code:     subtest "single node", sub {
        $simple->start();
        $simple->waitForUnit("etcd.service");
        $simple->waitUntilSucceeds("etcdctl set /foo/bar 'Hello world'");
        $simple->waitUntilSucceeds("etcdctl get /foo/bar | grep 'Hello world'");
      };
  
  