Added assertXML[Not]Equal assertions

This is especially needed to compare XML when hash randomization
is on, as attribute order may vary. Refs #17758, #19038.
Thanks Taylor Mitchell for the initial patch, and Ian Clelland for
review and cleanup.

tests/regressiontests/test_utils/tests.py

@@ -450,6 +450,41 @@ class HTMLEqualTests(TestCase):
         self.assertContains(response, '<p class="help">Some help text for the title (with unicode ŠĐĆŽćžšđ)</p>', html=True)
 
 
+class XMLEqualTests(TestCase):
+    def test_simple_equal(self):
+        xml1 = "<elem attr1='a' attr2='b' />"
+        xml2 = "<elem attr1='a' attr2='b' />"
+        self.assertXMLEqual(xml1, xml2)
+
+    def test_simple_equal_unordered(self):
+        xml1 = "<elem attr1='a' attr2='b' />"
+        xml2 = "<elem attr2='b' attr1='a' />"
+        self.assertXMLEqual(xml1, xml2)
+
+    def test_simple_equal_raise(self):
+        xml1 = "<elem attr1='a' />"
+        xml2 = "<elem attr2='b' attr1='a' />"
+        with self.assertRaises(AssertionError):
+            self.assertXMLEqual(xml1, xml2)
+
+    def test_simple_not_equal(self):
+        xml1 = "<elem attr1='a' attr2='c' />"
+        xml2 = "<elem attr1='a' attr2='b' />"
+        self.assertXMLNotEqual(xml1, xml2)
+
+    def test_simple_not_equal_raise(self):
+        xml1 = "<elem attr1='a' attr2='b' />"
+        xml2 = "<elem attr2='b' attr1='a' />"
+        with self.assertRaises(AssertionError):
+            self.assertXMLNotEqual(xml1, xml2)
+
+    def test_parsing_errors(self):
+        xml_unvalid = "<elem attr1='a attr2='b' />"
+        xml2 = "<elem attr2='b' attr1='a' />"
+        with self.assertRaises(AssertionError):
+            self.assertXMLNotEqual(xml_unvalid, xml2)
+
+
 class SkippingExtraTests(TestCase):
     fixtures = ['should_not_be_loaded.json']