private void testSplit(InputSplit split, byte[]... columns) throws Exception {
    WALRecordReader<WALKey> reader = getReader();
    reader.initialize(split, MapReduceTestUtil.createDummyMapTaskAttemptContext(conf));

    for (byte[] column : columns) {
      assertTrue(reader.nextKeyValue());
      Cell cell = reader.getCurrentValue().getCells().get(0);
      if (
        !Bytes.equals(column, 0, column.length, cell.getQualifierArray(), cell.getQualifierOffset(),
          cell.getQualifierLength())
      ) {
        assertTrue(
          "expected [" + Bytes.toString(column) + "], actual [" + Bytes.toString(
            cell.getQualifierArray(), cell.getQualifierOffset(), cell.getQualifierLength()) + "]",
          false);
      }
    }
    assertFalse(reader.nextKeyValue());
    reader.close();
  }
Create a new reader from the split, and match the edits against the passed columns.
hbase-mapreduce/src/test/java/org/apache/hadoop/hbase/mapreduce/TestWALRecordReader.java