CombineFileSplit split = new CombineFileSplit(files, lengths);
RecordReader rr = inputFormat.createRecordReader(split, context);
assertTrue("Unexpected RR type!", rr instanceof CombineFileRecordReader);
// first initialize() call comes from MapTask. We'll do it here.
rr.initialize(split, context);
// First value is first filename.
assertTrue(rr.nextKeyValue());
assertEquals("file1", rr.getCurrentValue().toString());