public void assertVisitWithValidNowWorks(String expression) throws ParseException {
        DocumentSelector selector = new DocumentSelector(expression);
        NowCheckVisitor visitor = new NowCheckVisitor();
        selector.visit(visitor);
        assertTrue(visitor.requiresConversion());
        SelectionExpressionConverter converter = new SelectionExpressionConverter();
        try {
            selector.visit(converter);
        } catch (Exception e) {
            assertFalse("Converter throws exception : " + e.getMessage(), true);
        }
    }
@author Simon Thoresen Hult
@author bratseth
document/src/test/java/com/yahoo/document/select/DocumentSelectorTestCase.java