### Question:
IdAddingSolrUpdateWriter implements SolrUpdateWriter { @Override public void deleteById(String documentId) { updateCollector.deleteById(documentId); } IdAddingSolrUpdateWriter(String uniqueKeyField, String documentId, String tableNameField, String tableName,
            SolrUpdateCollector updateCollector); @Override void add(SolrInputDocument solrDocument); @Override void deleteById(String documentId); @Override void deleteByQuery(String query);  }### Answer:
@Test public void testDeleteById() { IdAddingSolrUpdateWriter updateWriter = new IdAddingSolrUpdateWriter(UNIQUE_KEY_FIELD, DOCUMENT_ID, null, TABLE_NAME, updateCollector); updateWriter.deleteById(DOCUMENT_ID); verify(updateCollector).deleteById(DOCUMENT_ID); }