Official XSLT validator?

Is there any official XSLT validator, like http://validator.w3.org/ for HTML & XHTML?

I know http://validator.w3.org/ can also be used to validate XML and XSL documents. But they are validated as XML structures.

In valid XHTML, for example, <span><div>...</div></span> is invalid, as block elements should not appear inside in-line elements.

So, is there a convenient way, to directly validate the XSL document?

(i guess we may combine XML and XSL, output the XHTML, then validate it. But this is not directly and not convenient.)

Thanks!