@Test(expected = IOException.class)
public void testAdd_IOException() throws SolrServerException, IOException {

    
    SolrInputDocument inputDoc = mock(SolrInputDocument.class);
    Map<String, SolrInputDocument> inputDocMap = ImmutableMap.of("idA", inputDoc);
    when(solrServer.add(inputDocMap.values())).thenThrow(new IOException());
    solrWriter.add(-1, inputDocMap);
}