Python unittest.TestCase for XML testing using lxml.
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Python XML-Unittest

Anyone uses XML, for RSS, for configuration files, for... well, we all use XML for our own reasons (folk says one can not simply uses XML, but still...).

So, your code generates XML, and everything is fine. As you follow best practices (if you don’t, I think you should), you have written some good unit-tests, where you compare code’s result with an expected result. I mean you compare string with string. Do you see the issue here? If you don’t, well, good for you. I see a lot of issue with this approach.

XML is not a simple string, it is a structured document. One can not simply compare two XML string and expect all being fine: attributes’s order can change unexpectedly, elements can be optional, and no one can explain simply how spaces and tabs works in XML formatting.

Here comes XML unittest TestCase: if you want to use the built-in unittest package (or if it is a requirement), and you are not afraid of using xpath expression with lxml, this library is made for you.

You will be able to test your XML document, and use the power of xpath and various schema languages to write tests that matter.


How to

  • Extends xmlunittest.XmlTestCase
  • Write your tests, using the function or method that generate XML document
  • Use xmlunittest.XmlTestCase‘s assertion methods to validate
  • Keep your test readable


from xmlunittest import XmlTestCase

class CustomTestCase(XmlTestCase):

    def test_my_custom_test(self):
        # In a real case, data come from a call to your function/method.
        data = """<?xml version="1.0" encoding="UTF-8" ?>
        <root xmlns:ns="uri">
            <leaf id="1" active="on" />
            <leaf id="2" active="on" />
            <leaf id="3" active="off" />

        # Everything starts with `assertXmlDocument`
        root = self.assertXmlDocument(data)

        # Check namespace
        self.assertXmlNamespace(root, 'ns', 'uri')
        # Check
        self.assertXpathsUniqueValue(root, ('./leaf/@id', ))
        self.assertXpathValues(root, './leaf/@active', ('on', 'off'))