@Override
  public String getName() {
    return _name;
  }
@Test
  public void testStringLowerTransformFunctionNullColumn() {
    ExpressionContext expression =
        RequestContextUtils.getExpression(String.format("lower(%s)", STRING_ALPHANUM_NULL_SV_COLUMN));
    TransformFunction transformFunction = TransformFunctionFactory.get(expression, _dataSourceMap);
    assertTrue(transformFunction instanceof ScalarTransformFunctionWrapper);
    assertEquals(transformFunction.getName(), "lower");
    String[] expectedValues = new String[NUM_ROWS];
    RoaringBitmap bitmap = new RoaringBitmap();
    for (int i = 0; i < NUM_ROWS; i++) {
      if (isNullRow(i)) {
        bitmap.add(i);
      } else {
        expectedValues[i] = _stringAlphaNumericSVValues[i].toLowerCase();
      }
    }
    testTransformFunctionWithNull(transformFunction, expectedValues, bitmap);
  }