tests: add helper to check XML documents

tests/xml_utils.py

@@ -0,0 +1,15 @@
+from lxml import etree as ET
+
+
+def assert_xml_constraints(content, constraint, namespaces={}):
+    d = ET.fromstring(content)
+    def check(constraint, prefix=''):
+        path, count = constraint[:2]
+        path = prefix + path
+        if not count is None:
+            l = d.xpath(path, namespaces=namespaces)
+            assert len(l) == count, 'len(xpath(%s)) is not %s but %s' % (path, count, len(l))
+        if len(constraint) > 2:
+            for constraint in constraint[2:]:
+                check(constraint, prefix=path)
+    check(constraint)