IndexWriter writer = newWriter(dir, false);
writer.setMaxBufferedDocs(10);
writer.setMergeFactor(4);
addDocs(writer, 10);
writer.addIndexesNoOptimize(new Directory[] { aux });
assertEquals(1040, writer.docCount());
assertEquals(2, writer.getSegmentCount());
assertEquals(1000, writer.getDocCount(0));
writer.close();