code: public MockVolume createVolume(
              final String volumeType, final String size, final String availabilityZone,
              final int iops,
              final String snapshotId) {
  
          MockVolume ret = new MockVolume();
          ret.setVolumeType(volumeType);
          ret.setVolumeId(
                  "vol-" + UUID.randomUUID().toString().substring(0, VOLUME_ID_POSTFIX_LENGTH));
          ret.setSize(size);
          ret.setAvailabilityZone(availabilityZone);
          ret.setIops(iops);
          ret.setSnapshotId(snapshotId);
  
          allMockVolumes.put(ret.getVolumeId(), ret);
          return ret;
      }
docs: Create the mock Volume.
  @param volumeType of Volume.
  @param size : Volume size.
  @param availabilityZone : Volume availability zone.
  @param iops : Volume iops count
  @param snapshotId : Volume's SnapshotId.
  @return mock Volume.