Question on Microsoft's min-width-percentage-003.xht test

Hello,

Regarding

http://test.csswg.org/source/contributors/microsoft/submitted/Chapter_10/min-width-percentage-003.xht

I would like to understand why such test. If the test assert says

"
If the containing block's width depends on this element's width, then
the resulting layout is undefined.
"

(which is also what CSS 2.1 section 10.4
http://www.w3.org/TR/CSS21/visudet.html#min-max-widths
is saying)

then what is such test testing exactly? What's the point (value,
usefulness) of such test?

If the words "Filler Text" are not there in some user agent, then how
does such absence constitute a failure or some sort of spec violation?

Am I missing something?

regards, Gérard