jQuery, selct and click radio button

For radio buttons in HTML

     <input type="radio" name="test" id="test1" />test1<br/>
     <input type="radio" name="test" id="test2" />test2<br/>
     <input type="radio" name="test" id="test3" />test3</br>

To get selected value:

$('input:radio[name=test]:checked').val();

To perform an action when click the radio button

$(function(){

$('input:radio[name=test]').change(
    function(){
        alert('changed');   
    }
);          

});

To set the first button checked:

$('input:radio[name=test]:nth(0)').attr('checked',true);
or
$('input:radio[name=test]')[0].checked = true;