private void testStringValues() {
    ColumnBuffer stringColumn = new ColumnBuffer(Type.STRING_TYPE);
    stringColumn.addValue(Type.STRING_TYPE, "12abc456");
    stringColumn.addValue(Type.STRING_TYPE, "~special$&string");

    assertEquals(Type.STRING_TYPE, stringColumn.getType());
    assertEquals(2, stringColumn.size());
    assertEquals("12abc456", stringColumn.get(0));
    assertEquals("~special$&string", stringColumn.get(1));
  }
Test if the nulls BitSet is maintained properly when we extract subset from ColumnBuffer.
E.g. suppose we have a ColumnBuffer with nulls [0, 0, 1, 0]. When we split it evenly into
two subsets, the subsets should have nulls [0, 0] and [1, 0] respectively.
serde/src/test/org/apache/hadoop/hive/serde2/thrift/TestColumnBuffer.java