def test_invalid(self):
        """
        Test that invalid attributes are correctly loaded and written
        """
        doc = QDomDocument("properties")

        elem = QgsXmlUtils.writeVariant(None, doc)

        prop2 = QgsXmlUtils.readVariant(elem)
        self.assertIsNone(prop2)

    def test_list(self):
        """
        Test that lists are correctly loaded and written
        """
        doc = QDomDocument("properties")
        my_properties = [1, 4, 'a', 'test', 7.9]
        elem = QgsXmlUtils.writeVariant(my_properties, doc)

        prop2 = QgsXmlUtils.readVariant(elem)

        self.assertEqual(my_properties, prop2)

    def test_integer(self):
        """
        Test that maps are correctly loaded and written
        """
        doc = QDomDocument("properties")

        my_properties = {'a': 1, 'b': 2, 'c': 3, 'd': -1}
        elem = QgsXmlUtils.writeVariant(my_properties, doc)

        prop2 = QgsXmlUtils.readVariant(elem)
        self.assertEqual(my_properties, prop2)

    def test_geom(self):
        """
        Test that QgsGeometry values are correctly loaded and written
        """
        doc = QDomDocument("properties")

        g = QgsGeometry.fromWkt('Point(3 4)')
        elem = QgsXmlUtils.writeVariant(g, doc)

        g2 = QgsXmlUtils.readVariant(elem)
        self.assertEqual(g2.asWkt(), 'Point (3 4)')

    def test_boolean(self):
        """
        Test that maps are correctly loaded and written
        """
        doc = QDomDocument("properties")

        my_properties = {'a': True, 'b': False}
        elem = QgsXmlUtils.writeVariant(my_properties, doc)

        prop2 = QgsXmlUtils.readVariant(elem)

        self.assertEqual(my_properties, prop2)

    def test_double(self):
        """
        Test that maps are correctly loaded and written
        """
        doc = QDomDocument("properties")

        my_properties = {'a': 0.27, 'b': 1.0, 'c': 5}
        elem = QgsXmlUtils.writeVariant(my_properties, doc)

        prop2 = QgsXmlUtils.readVariant(elem)

        self.assertEqual(my_properties, prop2)

    def test_string(self):
        """
        Test that maps are correctly loaded and written
        """
        doc = QDomDocument("properties")

        my_properties = {'a': 'a', 'b': 'b', 'c': 'something_else', 'empty': ''}
        elem = QgsXmlUtils.writeVariant(my_properties, doc)

        prop2 = QgsXmlUtils.readVariant(elem)

        self.assertEqual(my_properties, prop2)

    def test_long(self):
        """
        Test that maps are correctly loaded and written
        """
        doc = QDomDocument("properties")

        # not sure if this actually does map to a long?
        my_properties = {'a': 9223372036854775808}
        elem = QgsXmlUtils.writeVariant(my_properties, doc)

        prop2 = QgsXmlUtils.readVariant(elem)
        self.assertEqual(my_properties, prop2)

    def test_crs(self):
        """
        Test that QgsCoordinateReferenceSystem values are correctly loaded and written
        """
        doc = QDomDocument("properties")

        crs = QgsCoordinateReferenceSystem('epsg:3111')
        elem = QgsXmlUtils.writeVariant(crs, doc)

        crs2 = QgsXmlUtils.readVariant(elem)
        self.assertTrue(crs2.isValid())
        self.assertEqual(crs2.authid(), 'EPSG:3111')

        crs = QgsCoordinateReferenceSystem()
        elem = QgsXmlUtils.writeVariant(crs, doc)

        crs2 = QgsXmlUtils.readVariant(elem)
        self.assertFalse(crs2.isValid())