### Question:
BufferedSolrInputDocumentWriter implements SolrInputDocumentWriter { @Override public void deleteById(int shard, List<String> idsToDelete) throws SolrServerException, IOException { delegateWriter.deleteById(shard, idsToDelete); } BufferedSolrInputDocumentWriter(SolrInputDocumentWriter delegateWriter, int bufferSize,
            Counter documentOutputCounter, Counter documentBatchOutputCounter); @Override void add(int shard, Map<String, SolrInputDocument> inputDocumentMap); @Override void deleteById(int shard, List<String> idsToDelete); @Override void deleteByQuery(String deleteQuery); void flush(); @Override void close();  }### Answer:
@Test public void testDeleteById() throws SolrServerException, IOException { bufferedWriter.deleteById(-1, ImmutableList.of("a")); verify(delegateWriter).deleteById(eq(-1), eq(ImmutableList.of("a"))); }