jQuery - fadeIn -fadeOut -fadeToggle and fadeTo

HTML

<p><button id="in">fadeIn()</button>
<button id="out">fadeOut()</button>
<button id="toggle">fadeToggle()</button>
<button id="to">fadeTo()</button></p>

<div id="test"></div>

CSS

#test {
    margin: 3em auto;
    width: 15em;
    height: 3em;
    background: blue;
}

JavaScript

var test = $('#test'),
    $in = $('#in'),
    out = $('#out'),
    toggle = $('#toggle'),
    to = $('#to');


$in.click(function() {
    test.fadeIn(1000, function() {
    });
});
    
    
out.click(function() {
    test.fadeOut(1000, function() {
    });
});


toggle.click(function() {
    test.fadeToggle(5000, function() {
    });
});

to.click(function() {
    test.fadeTo(1000, 0.1, function() {
    });
});