This test fails because it expects a MIME type "Content-Type: image/gif"
whereas that provided by libmagic is "Content-Type: image/gif; charset=binary"
Presumably the test was written against a different version.
--- aegis-4.24/test/02/t0228a-matt.sh	2008-03-14 07:19:27.000000000 +0100
+++ aegis-4.24/test/02/t0228a-matt.sh	2014-01-27 09:43:44.000000000 +0100
@@ -147,7 +147,8 @@
 SCRIPT_NAME=/cgi-bin/aeget \
 PATH_INFO=icon/rss.gif \
 QUERY_STRING= \
-$bin/aeget > rss.served.gif 2>&1
+$bin/aeget \
+| sed -e 's%^Content-Type: image/gif; charset=binary%Content-Type: image/gif%' > rss.served.gif 2>&1
 if test $? -ne 0 ; then fail; fi
 
 # Compare the expected and the actual received file.
lect name='h' onchange='this.form.submit();'>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
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<option value='committer'>committer</option>
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<input class='txt' type='search' size='10' name='q' value=''/>
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<div class='path'>path: <a href='/guix/log/?id=903718659a1ceb07308d19f7236d6423488a300b'>root</a>/<a href='/guix/log/gnu?id=903718659a1ceb07308d19f7236d6423488a300b'>gnu</a>/<a href='/guix/log/gnu/packages?id=903718659a1ceb07308d19f7236d6423488a300b'>packages</a>/<a href='/guix/log/gnu/packages/medical.scm?id=903718659a1ceb07308d19f7236d6423488a300b'>medical.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/medical.scm?id=903718659a1ceb07308d19f7236d6423488a300b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-03-20 23:46:16 -0400'>2023-03-20</span></td><td><a href='/guix/commit/gnu/packages/medical.scm?id=ac6e5d5b8006ddd455a40d32e59f877c75f4ca21'>gnu: Add mygnuhealth.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/medical.scm (mygnuhealth): New variable.

Signed-off-by: Maxim Cournoyer &lt;maxim.cournoyer@gmail.com&gt;
Co-authored-by: Morgan Smith &lt;Morgan.J.Smith@outlook.com&gt;
Modified-by: Maxim Cournoyer &lt;maxim.cournoyer@gmail.com&gt;
</span></span></td><td>Petr Hodina</td></tr>