> how can i extract "test" from <value><![CDATA[test]]></value>?

In exactly the same way as from <value>test</value>. The CDATA makes no
difference, it's just wasted bandwidth.
 
> The problem is that i don't know how many 
> <value><![CDATA[test]]></value> there will be, so i can't use 
> variables.

A curious statement. You don't need variables, but the fact that you have
multiple occurrences is no obstacle to using variables. A variable can hold
a node-set.


> I know that <xsl:value-of select="value" /> works, but i need 
> the result of extraction in my comparison with another
> attribute and you can't say: <xsl:if test="@id = 
> <xsl:value-of select="value" />">.
> 

Sometimes people make things far more difficult than they are.

<xsl:if test="@id = value">

will test if the @id attribute of the current element is equal to the
content of any <value> element child of the current element.

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