def test_duplicate_slug(self):
        try:
            from wagtail.core.models import Site
        except ImportError:
            from wagtail.wagtailcore.models import Site
        # Create a test Site with a root page
        root = models.TestRootPage(title='title', depth=1, path='0001', slug_en='slug_en', slug_de='slug_de')
        root.save()

        site = Site(root_page=root)
        site.save()

        # Add children to the root
        child = root.add_child(
            instance=models.TestSlugPage1(title='child1', slug_de='child', slug_en='child-en', depth=2, path='00010001')
        )

        child2 = root.add_child(
            instance=models.TestSlugPage2(title='child2', slug_de='child-2', slug_en='child2-en', depth=2,
                                          path='00010002')
        )

        # Clean should work fine as the two slugs are different
        child2.clean()

        # Make the slug equal to test if the duplicate is detected
        child2.slug_de = 'child'
        self.assertRaises(ValidationError, child2.clean)
        child2.slug_de = 'child-2'

        # Make the translated slug equal to test if the duplicate is detected
        child2.slug_en = 'child-en'
        self.assertRaises(ValidationError, child2.clean)

def root_page():
    """
    Get the global Wagtail root page (cleared of any subpages it might have)
    :return: Root page
    :rtype: wagtail.wagtailcore.models.Page
    """
    try:
        page = Page.objects.get(slug="root", depth=1)
    except Page.DoesNotExist:  # pragma: no cover
        page = Page.objects.create(
            title="Root",
            slug='root',
            content_type=ContentType.objects.get_for_model(Page),
            path='0001',
            depth=1,
            numchild=1,
            url_path='/',
        )

    for child in page.get_children():  # pragma: no cover
        child.delete()
    page.numchild = 0
    page.save(update_fields=("numchild",))

    site = Site.objects.first()
    if not site:  # pragma: no cover
        site = Site()
    site.root_page = page
    site.is_default_site = True
    site.save()

    return page