@Override
    public Committer closeForCommit() throws IOException {
        lock();
        try {
            uploadCurrentPart();
            return upload.getCommitter();
        } finally {
            unlock();
        }
    }
@Test
    public void testNoDataWritten() throws IOException {
        RecoverableFsDataOutputStream.Committer committer = fsDataOutputStream.closeForCommit();
        committer.commit();

        // will not create empty object
        assertFalse(fs.exists(objectPath));
    }