it('should reset maxDate to +Infinity when set empty string', function() {
        var elm = compileDirective('options-maxDate');
        angular.element(elm[0]).triggerHandler('focus');
        expect(sandboxEl.find('.dropdown-menu tbody button:contains(24)').is(':disabled')).toBeFalsy();
        expect(sandboxEl.find('.dropdown-menu tbody button:contains(25)').is(':disabled')).toBeTruthy();