Getting multiple attribute values from XML via xpath

I'm trying to retrieve multiple attribute values (foo and bar) with one single xpath query.

This is my XML content (test.xml):

<root>
    <level1>
        <child foo="bar" bar="foo" />
    </level1>
</root>

Current best solution based on:

• Getting attribute value from XML in bash script with XPath string()
• https://unix.stackexchange.com/questions/52711/xmllint-display-values-of-more-than-1-attributes-in-single-execution
• ..and a lot of googling

xmllint test.xml --xpath '//root/level1/child/@*[name()="foo" or name()="bar"]'
xpath -q -e '//root/level1/child/@*[name()="foo" or name()="bar"]' test.xml

..which both return:

 foo="bar"
 bar="foo"

However I would like to have an output similar this (attribute names and =" removed):

bar
foo

Wrapping the query with string() sadly doesn't work.

Is it actually possible to get multiple attribute values at once, or am I trying something impossible?

I'm aware that I could pipe the output through cut or awk but that isn't possible in the actual environment.