Fix gzip RDF/XML test: create item and append data instead of testing root container

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: namedgraph

http-tests/misc/gzip-rdfxml.sh

@@ -7,13 +7,39 @@ purge_cache "$END_USER_VARNISH_SERVICE"
 purge_cache "$ADMIN_VARNISH_SERVICE"
 purge_cache "$FRONTEND_VARNISH_SERVICE"
 
-# Test that nginx gzip compression is active for RDF/XML dynamic content
+# Test that nginx gzip compression is active for RDF/XML dynamic content.
+# Create an item, append enough data to exceed gzip_min_length, then retrieve it as RDF/XML.
+
+add-agent-to-group.sh \
+  -f "$OWNER_CERT_FILE" \
+  -p "$OWNER_CERT_PWD" \
+  --agent "$AGENT_URI" \
+  "${ADMIN_BASE_URL}acl/groups/writers/"
+
+item=$(create-item.sh \
+  -f "$AGENT_CERT_FILE" \
+  -p "$AGENT_CERT_PWD" \
+  -b "$END_USER_BASE_URL" \
+  --title "Gzip test item" \
+  --slug "gzip-test" \
+  --container "$END_USER_BASE_URL")
+
+printf '@prefix ex: <http://example.org/> .\n
+<> ex:prop1 "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore." ;\n
+   ex:prop2 "Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo." ;\n
+   ex:prop3 "Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur." ;\n
+   ex:prop4 "Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est." .\n' \
+| post.sh \
+  -f "$AGENT_CERT_FILE" \
+  -p "$AGENT_CERT_PWD" \
+  -t "text/turtle" \
+  "$item"
 
 response=$(curl -k -s -D - -o /dev/null \
   -H "Accept-Encoding: gzip" \
   -H "Accept: application/rdf+xml" \
-  --cert "$OWNER_CERT_FILE:$OWNER_CERT_PWD" \
-  "$END_USER_BASE_URL")
+  -E "$AGENT_CERT_FILE":"$AGENT_CERT_PWD" \
+  "$item")
 
 if ! echo "$response" | grep -qi "Content-Encoding: gzip"; then
   echo "Content-Encoding: gzip not found on RDF/XML response"