/*
  * Test the visitor passing interface.
  */
 @Test
 public void testVisitorFunctionsFilter() {
   String expected = "a eq " + Relation.SUBSTR.getoDataString() + "(a, b, c)";
   String actual =
       ODataParser.toFilters(ODataParser.parseFilters(expected), new OutputExpressionVisitor());
   assertEquals(expected, actual);
 }
 /*
  * Test a few special function.
  */
 @Test
 public void testSpecialFunctionsFilter() {
   // Substr can also be called with 3 args
   testValid("a eq " + Relation.SUBSTR.getoDataString() + "(a, b, c)");
 }