// Fires up an instance, finds its root volume ID, takes a snapshot, then
  // terminates the instance.
  private Snapshot createSnapshot() throws RunNodesException {

    String instanceId = null;
    try {
      RunningInstance instance =
          getOnlyElement(
              concat(
                  ec2Client
                      .getInstanceServices()
                      .runInstancesInRegion(regionId, null, imageId, 1, 1)));
      instanceId = instance.getId();

      assertTrue(runningTester.apply(instance), instanceId + "didn't achieve the state running!");

      instance =
          getOnlyElement(
              concat(
                  ec2Client.getInstanceServices().describeInstancesInRegion(regionId, instanceId)));
      BlockDevice device = instance.getEbsBlockDevices().get("/dev/sda1");
      assertNotNull(device, "device: /dev/sda1 not present on: " + instance);
      Snapshot snapshot =
          ec2Client
              .getElasticBlockStoreServices()
              .createSnapshotInRegion(regionId, device.getVolumeId());
      snapshotsToDelete.add(snapshot.getId());
      return snapshot;
    } finally {
      if (instanceId != null)
        ec2Client.getInstanceServices().terminateInstancesInRegion(regionId, instanceId);
    }
  }
 @Override
 @AfterClass(groups = {"integration", "live"})
 protected void tearDownContext() {
   for (String imageId : imagesToDeregister) client.deregisterImageInRegion(regionId, imageId);
   for (String snapshotId : snapshotsToDelete)
     ec2Client.getElasticBlockStoreServices().deleteSnapshotInRegion(regionId, snapshotId);
   super.tearDownContext();
 }