### Question:
SolrInputDocumentBuilder { public void add(SolrInputDocument inputDocument) { add(inputDocument, ""); } SolrInputDocumentBuilder();  SolrInputDocumentBuilder(SolrInputDocument baseDocument); void add(SolrInputDocument inputDocument); void add(SolrInputDocument inputDocument, String prefix); SolrInputDocument getDocument();  }### Answer:
@Test public void testAdd() { SolrInputDocumentBuilder builder = new SolrInputDocumentBuilder(); SolrInputDocument docA = new SolrInputDocument(); SolrInputDocument docB = new SolrInputDocument(); docA.addField("fieldA", "valueA1"); docA.addField("fieldA", "valueA2"); docB.addField("fieldB", "valueB"); builder.add(docA); builder.add(docB); SolrInputDocument merged = builder.getDocument(); assertEquals(Sets.newHashSet("fieldA", "fieldB"), merged.keySet()); assertEquals(Lists.newArrayList("valueA1", "valueA2"), merged.getField("fieldA").getValues()); assertEquals(Lists.newArrayList("valueB"), merged.getField("fieldB").getValues()); }