private void assertTrimFunction(
          ASTNode tree, String expectedFunctionName, String expectedStringToTrim) {
    assertTrimFunction(tree, expectedFunctionName, expectedStringToTrim, 2);
  }
Test cases for parse WITHIN GROUP clause syntax.
function(expression) WITHIN GROUP (ORDER BY sort_expression)
parser/src/test/org/apache/hadoop/hive/ql/parse/TestParseTrim.java