RegexFieldValidator validator = new RegexFieldValidator();
validator.setExpression("^Sec.*");
validator.setValidatorContext(new GenericValidatorContext(new Object()));
validator.setFieldName("username");
validator.setValueStack(ActionContext.getContext().getValueStack());
validator.validate(testPerson);
assertFalse(validator.getValidatorContext().hasErrors());
assertFalse(validator.getValidatorContext().hasActionErrors());
assertFalse(validator.getValidatorContext().hasActionMessages());
assertFalse(validator.getValidatorContext().hasFieldErrors());