Refs #34041 -- Added navigation landmark to breadcrumbs in admin.

Thanks Thibaud Colas for pair programming.

tests/admin_views/test_breadcrumbs.py

@@ -0,0 +1,25 @@
+from django.contrib.auth.models import User
+from django.test import TestCase, override_settings
+from django.urls import reverse
+
+
+@override_settings(ROOT_URLCONF="admin_views.urls")
+class AdminBreadcrumbsTests(TestCase):
+    @classmethod
+    def setUpTestData(cls):
+        cls.superuser = User.objects.create_superuser(
+            username="super",
+            password="secret",
+            email="super@example.com",
+        )
+
+    def setUp(self):
+        self.client.force_login(self.superuser)
+
+    def test_breadcrumbs_absent(self):
+        response = self.client.get(reverse("admin:index"))
+        self.assertNotContains(response, '<nav aria-label="Breadcrumbs">')
+
+    def test_breadcrumbs_present(self):
+        response = self.client.get(reverse("admin:auth_user_add"))
+        self.assertContains(response, '<nav aria-label="Breadcrumbs">')