diff --git a/swh/indexer/tests/test_metadata.py b/swh/indexer/tests/test_metadata.py
--- a/swh/indexer/tests/test_metadata.py
+++ b/swh/indexer/tests/test_metadata.py
@@ -7,7 +7,6 @@
 import unittest
 
 from hypothesis import given, strategies, settings, HealthCheck
-import xmltodict
 
 from swh.model.hashutil import hash_to_bytes
 
@@ -23,7 +22,8 @@
 
 from .utils import (
     BASE_TEST_CONFIG, fill_obj_storage, fill_storage,
-    YARN_PARSER_METADATA, json_document_strategy
+    YARN_PARSER_METADATA, json_document_strategy,
+    xml_document_strategy,
 )
 
 
@@ -1086,11 +1086,12 @@
         self.codemeta_mapping.translate(raw)
 
     @settings(suppress_health_check=[HealthCheck.too_slow])
-    @given(json_document_strategy(
-        keys=list(MAPPINGS['MavenMapping'].mapping)))
+    @given(xml_document_strategy(
+        keys=list(MAPPINGS['MavenMapping'].mapping),
+        root='project',
+        xmlns='http://maven.apache.org/POM/4.0.0'))
     def test_maven_adversarial(self, doc):
-        raw = xmltodict.unparse({'project': doc}, pretty=True)
-        self.maven_mapping.translate(raw)
+        self.maven_mapping.translate(doc)
 
     @settings(suppress_health_check=[HealthCheck.too_slow])
     @given(strategies.dictionaries(
diff --git a/swh/indexer/tests/utils.py b/swh/indexer/tests/utils.py
--- a/swh/indexer/tests/utils.py
+++ b/swh/indexer/tests/utils.py
@@ -432,7 +432,7 @@
 
 def json_document_strategy(keys=None):
     """Generates an hypothesis strategy that generates metadata files
-    for a format that uses the given keys."""
+    for a JSON-based format that uses the given keys."""
     if keys is None:
         keys = strategies.characters()
     else:
@@ -441,6 +441,40 @@
     return strategies.dictionaries(keys, generic_json_document, min_size=1)
 
 
+def xml_document_strategy(keys, root, xmlns):
+    """Generates an hypothesis strategy that generates metadata files
+    for an XML format that uses the given keys."""
+    def encode(s):
+        "Skips unpaired surrogates generated by json_document_strategy"
+        return s.encode('utf8', 'replace')
+
+    def to_xml(data, indent=b' '):
+        if data is None:
+            return b''
+        elif isinstance(data, (bool, str, int, float)):
+            return encode(str(data))
+        elif isinstance(data, list):
+            return b'\n'.join(to_xml(v, indent=indent) for v in data)
+        elif isinstance(data, dict):
+            lines = []
+            for (key, value) in data.items():
+                lines.append(indent + encode('<{}>'.format(key)))
+                lines.append(indent + to_xml(value, indent=indent+b' '))
+                lines.append(indent + encode('</{}>'.format(key)))
+            return b'\n'.join(lines)
+        else:
+            raise TypeError(data)
+
+    def to_root_xml(data):
+        return b'\n'.join([
+            '<{} xmlns="{}">'.format(root, xmlns).encode(),
+            to_xml(data),
+            '</{}>'.format(root).encode(),
+        ])
+
+    return strategies.builds(to_root_xml, json_document_strategy(keys))
+
+
 def filter_dict(d, keys):
     'return a copy of the dict with keys deleted'
     if not isinstance(keys, (list, tuple)):