@Test
  public void testKeyOnlyFilter() throws Exception {

    // KVs in first 6 rows
    KeyValue[] expectedKVs = {
      // testRowOne-0
      new KeyValue(ROWS_ONE[0], FAMILIES[0], QUALIFIERS_ONE[0], VALUES[0]),
      new KeyValue(ROWS_ONE[0], FAMILIES[0], QUALIFIERS_ONE[2], VALUES[0]),
      new KeyValue(ROWS_ONE[0], FAMILIES[0], QUALIFIERS_ONE[3], VALUES[0]),
      new KeyValue(ROWS_ONE[0], FAMILIES[1], QUALIFIERS_ONE[0], VALUES[0]),
      new KeyValue(ROWS_ONE[0], FAMILIES[1], QUALIFIERS_ONE[2], VALUES[0]),
      new KeyValue(ROWS_ONE[0], FAMILIES[1], QUALIFIERS_ONE[3], VALUES[0]),
      // testRowOne-2
      new KeyValue(ROWS_ONE[2], FAMILIES[0], QUALIFIERS_ONE[0], VALUES[0]),
      new KeyValue(ROWS_ONE[2], FAMILIES[0], QUALIFIERS_ONE[2], VALUES[0]),
      new KeyValue(ROWS_ONE[2], FAMILIES[0], QUALIFIERS_ONE[3], VALUES[0]),
      new KeyValue(ROWS_ONE[2], FAMILIES[1], QUALIFIERS_ONE[0], VALUES[0]),
      new KeyValue(ROWS_ONE[2], FAMILIES[1], QUALIFIERS_ONE[2], VALUES[0]),
      new KeyValue(ROWS_ONE[2], FAMILIES[1], QUALIFIERS_ONE[3], VALUES[0]),
      // testRowOne-3
      new KeyValue(ROWS_ONE[3], FAMILIES[0], QUALIFIERS_ONE[0], VALUES[0]),
      new KeyValue(ROWS_ONE[3], FAMILIES[0], QUALIFIERS_ONE[2], VALUES[0]),
      new KeyValue(ROWS_ONE[3], FAMILIES[0], QUALIFIERS_ONE[3], VALUES[0]),
      new KeyValue(ROWS_ONE[3], FAMILIES[1], QUALIFIERS_ONE[0], VALUES[0]),
      new KeyValue(ROWS_ONE[3], FAMILIES[1], QUALIFIERS_ONE[2], VALUES[0]),
      new KeyValue(ROWS_ONE[3], FAMILIES[1], QUALIFIERS_ONE[3], VALUES[0]),
      // testRowTwo-0
      new KeyValue(ROWS_TWO[0], FAMILIES[0], QUALIFIERS_TWO[0], VALUES[1]),
      new KeyValue(ROWS_TWO[0], FAMILIES[0], QUALIFIERS_TWO[2], VALUES[1]),
      new KeyValue(ROWS_TWO[0], FAMILIES[0], QUALIFIERS_TWO[3], VALUES[1]),
      new KeyValue(ROWS_TWO[0], FAMILIES[1], QUALIFIERS_TWO[0], VALUES[1]),
      new KeyValue(ROWS_TWO[0], FAMILIES[1], QUALIFIERS_TWO[2], VALUES[1]),
      new KeyValue(ROWS_TWO[0], FAMILIES[1], QUALIFIERS_TWO[3], VALUES[1]),
      // testRowTwo-2
      new KeyValue(ROWS_TWO[2], FAMILIES[0], QUALIFIERS_TWO[0], VALUES[1]),
      new KeyValue(ROWS_TWO[2], FAMILIES[0], QUALIFIERS_TWO[2], VALUES[1]),
      new KeyValue(ROWS_TWO[2], FAMILIES[0], QUALIFIERS_TWO[3], VALUES[1]),
      new KeyValue(ROWS_TWO[2], FAMILIES[1], QUALIFIERS_TWO[0], VALUES[1]),
      new KeyValue(ROWS_TWO[2], FAMILIES[1], QUALIFIERS_TWO[2], VALUES[1]),
      new KeyValue(ROWS_TWO[2], FAMILIES[1], QUALIFIERS_TWO[3], VALUES[1]),
      // testRowTwo-3
      new KeyValue(ROWS_TWO[3], FAMILIES[0], QUALIFIERS_TWO[0], VALUES[1]),
      new KeyValue(ROWS_TWO[3], FAMILIES[0], QUALIFIERS_TWO[2], VALUES[1]),
      new KeyValue(ROWS_TWO[3], FAMILIES[0], QUALIFIERS_TWO[3], VALUES[1]),
      new KeyValue(ROWS_TWO[3], FAMILIES[1], QUALIFIERS_TWO[0], VALUES[1]),
      new KeyValue(ROWS_TWO[3], FAMILIES[1], QUALIFIERS_TWO[2], VALUES[1]),
      new KeyValue(ROWS_TWO[3], FAMILIES[1], QUALIFIERS_TWO[3], VALUES[1]) };

    // Grab all 6 rows
    long expectedRows = 6;
    long expectedKeys = this.colsPerRow;
    for (boolean useLen : new boolean[] { false, true }) {
      Scan s = new Scan();
      s.setFilter(new KeyOnlyFilter(useLen));
      verifyScan(s, expectedRows, expectedKeys);
      verifyScanFullNoValues(s, expectedKVs, useLen);
    }
  }
Tests the the {@link WhileMatchFilter} works in combination with a {@link Filter} that uses the
{@link Filter#filterCell(Cell)} method. See HBASE-2258.
hbase-server/src/test/java/org/apache/hadoop/hbase/filter/TestFilter.java