> Test Element
> <xsl:if test="number(test)">
> test is a number
> </xsl:if>
> 
> Test Attribute
> <xsl:if test="number(test/@test)">
> test attribute is a number
> </xsl:if>

That tests whether it's a non-zero number, which isn't what was asked for.

Michael Kay
http://www.saxonica.com/