@Override
  public String getName() {
    return _name;
  }
@Test
  public void testStringLowerTransformFunctionNullLiteral() {
    ExpressionContext expression =
        RequestContextUtils.getExpression("lower(null)");
    TransformFunction transformFunction = TransformFunctionFactory.get(expression, _dataSourceMap);
    assertTrue(transformFunction instanceof ScalarTransformFunctionWrapper);
    assertEquals(transformFunction.getName(), "lower");
    String[] expectedValues = new String[NUM_ROWS];
    RoaringBitmap bitmap = new RoaringBitmap();
    bitmap.add(0L, NUM_ROWS);
    testTransformFunctionWithNull(transformFunction, expectedValues, bitmap);
  }