Checking CSS Linear gradient support

Checking CSS Linear gradient support

Support for CSS properties(border-radius here) can be checked by this code:
if(document.createElement('test').style.borderRadius===''){
//some code
}
but what do I do in case of linear gradients? The declaration being like:
background:linear-gradient(top,bottom,#123,#456);
P.S. I don't want to use Modernizr. I want to learn how-to do this.