@Override
  public UnderFileSystem create(String path, UnderFileSystemConfiguration conf) {
    Preconditions.checkNotNull(path, "Unable to create UnderFileSystem instance:"
        + " URI path should not be null");

    try {
      return S3AUnderFileSystem.createInstance(new AlluxioURI(path), conf);
    } catch (AmazonClientException e) {
      throw Throwables.propagate(e);
    }
  }
@Test
  public void createInstanceWithNullPath() {
    Exception e = assertThrows(NullPointerException.class, () -> mFactory1.create(
        null, mConf));
    assertTrue(e.getMessage().contains("Unable to create UnderFileSystem instance: URI "
        + "path should not be null"));
  }