Refs #35189 -- Improved admin fieldset's accessibility by setting aria-labelledby.

Before this change, HTML <fieldset> elements in the admin site did not
have an associated label to describe them. This commit defines a unique
HTML id for the heading labeling a fieldset, and sets its
aria-labelledby property to link the heading with the fieldset.

3 files changed, 451 insertions, 44 deletions

diff --git a/tests/admin_inlines/admin.py b/tests/admin_inlines/admin.py
index 0ec56d71b3..3cdaee22df 100644
--- a/tests/admin_inlines/admin.py
+++ b/tests/admin_inlines/admin.py
@@ -40,6 +40,8 @@ from .models import (
     OutfitItem,
     ParentModelWithCustomPk,
     Person,
+    Photo,
+    Photographer,
     Poll,
     Profile,
     ProfileCollection,
@@ -98,6 +100,57 @@ class AuthorAdmin(admin.ModelAdmin):
     ]
 
 
+class PhotoInlineMixin:
+    model = Photo
+    extra = 2
+    fieldsets = [
+        (None, {"fields": ["image", "title"]}),
+        (
+            "Details",
+            {"fields": ["description", "creation_date"], "classes": ["collapse"]},
+        ),
+        (
+            "Details",  # Fieldset name intentionally duplicated
+            {"fields": ["update_date", "updated_by"]},
+        ),
+    ]
+
+
+class PhotoTabularInline(PhotoInlineMixin, admin.TabularInline):
+    pass
+
+
+class PhotoStackedExtra2Inline(PhotoInlineMixin, admin.StackedInline):
+    pass
+
+
+class PhotoStackedExtra3Inline(PhotoInlineMixin, admin.StackedInline):
+    extra = 3
+
+
+class PhotoStackedCollapsibleInline(PhotoInlineMixin, admin.StackedInline):
+    fieldsets = []
+    classes = ["collapse"]
+
+
+class PhotographerAdmin(admin.ModelAdmin):
+    fieldsets = [
+        (None, {"fields": ["firstname", "fullname"]}),
+        ("Advanced options", {"fields": ["nationality", "residency"]}),
+        (
+            "Advanced options",  # Fieldset name intentionally duplicated
+            {"fields": ["siblings", "children"], "classes": ["collapse"]},
+        ),
+    ]
+    inlines = [
+        PhotoTabularInline,
+        PhotoTabularInline,
+        PhotoStackedExtra2Inline,
+        PhotoStackedExtra3Inline,
+        PhotoStackedCollapsibleInline,
+    ]
+
+
 class InnerInline(admin.StackedInline):
     model = Inner
     can_delete = False
@@ -454,6 +507,7 @@ site.register(Teacher, TeacherAdmin)
 site.register(Chapter, inlines=[FootNoteNonEditableInlineCustomForm])
 site.register(OutfitItem, inlines=[WeaknessInlineCustomForm])
 site.register(Person, inlines=[AuthorTabularInline, FashonistaStackedInline])
+site.register(Photographer, PhotographerAdmin)
 site.register(Course, ClassAdminStackedHorizontal)
 site.register(CourseProxy, ClassAdminStackedVertical)
 site.register(CourseProxy1, ClassAdminTabularVertical)
diff --git a/tests/admin_inlines/models.py b/tests/admin_inlines/models.py
index eca5bae422..5a85556a55 100644
--- a/tests/admin_inlines/models.py
+++ b/tests/admin_inlines/models.py
@@ -180,6 +180,27 @@ class ShoppingWeakness(models.Model):
     item = models.ForeignKey(OutfitItem, models.CASCADE)
 
 
+# Models for #35189
+
+
+class Photographer(Person):
+    fullname = models.CharField(max_length=100)
+    nationality = models.CharField(max_length=100)
+    residency = models.CharField(max_length=100)
+    siblings = models.IntegerField()
+    children = models.IntegerField()
+
+
+class Photo(models.Model):
+    photographer = models.ForeignKey(Photographer, on_delete=models.CASCADE)
+    image = models.CharField(max_length=100)
+    title = models.CharField(max_length=100)
+    description = models.TextField()
+    creation_date = models.DateField()
+    update_date = models.DateField()
+    updated_by = models.CharField(max_length=100)
+
+
 # Models for #13510
 
 
diff --git a/tests/admin_inlines/tests.py b/tests/admin_inlines/tests.py
index 9533cc9af3..7b38619cc0 100644
--- a/tests/admin_inlines/tests.py
+++ b/tests/admin_inlines/tests.py
@@ -117,7 +117,14 @@ class TestInline(TestDataMixin, TestCase):
         "Autogenerated many-to-many inlines are displayed correctly (#13407)"
         response = self.client.get(reverse("admin:admin_inlines_author_add"))
         # The heading for the m2m inline block uses the right text
-        self.assertContains(response, "<h2>Author-book relationships</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="Author_books-heading" class="inline-heading">'
+                "Author-book relationships</h2>"
+            ),
+            html=True,
+        )
         # The "add another" label is correct
         self.assertContains(response, "Add another Author-book relationship")
         # The '+' is dropped from the autogenerated form prefix (Author_books+)
@@ -737,13 +744,35 @@ class TestInline(TestDataMixin, TestCase):
 
     def test_inlines_plural_heading_foreign_key(self):
         response = self.client.get(reverse("admin:admin_inlines_holder4_add"))
-        self.assertContains(response, "<h2>Inner4 stackeds</h2>", html=True)
-        self.assertContains(response, "<h2>Inner4 tabulars</h2>", html=True)
+        self.assertContains(
+            response,
+            (
+                '<h2 id="inner4stacked_set-heading" class="inline-heading">'
+                "Inner4 stackeds</h2>"
+            ),
+            html=True,
+        )
+        self.assertContains(
+            response,
+            (
+                '<h2 id="inner4tabular_set-heading" class="inline-heading">'
+                "Inner4 tabulars</h2>"
+            ),
+            html=True,
+        )
 
     def test_inlines_singular_heading_one_to_one(self):
         response = self.client.get(reverse("admin:admin_inlines_person_add"))
-        self.assertContains(response, "<h2>Author</h2>", html=True)  # Tabular.
-        self.assertContains(response, "<h2>Fashionista</h2>", html=True)  # Stacked.
+        self.assertContains(
+            response,
+            '<h2 id="author-heading" class="inline-heading">Author</h2>',
+            html=True,
+        )  # Tabular.
+        self.assertContains(
+            response,
+            '<h2 id="fashionista-heading" class="inline-heading">Fashionista</h2>',
+            html=True,
+        )  # Stacked.
 
     def test_inlines_based_on_model_state(self):
         parent = ShowInlineParent.objects.create(show_inlines=False)
@@ -914,28 +943,50 @@ class TestInlinePermissions(TestCase):
     def test_inline_add_m2m_noperm(self):
         response = self.client.get(reverse("admin:admin_inlines_author_add"))
         # No change permission on books, so no inline
-        self.assertNotContains(response, "<h2>Author-book relationships</h2>")
+        self.assertNotContains(
+            response,
+            (
+                '<h2 id="Author_books-heading" class="inline-heading">'
+                "Author-book relationships</h2>"
+            ),
+            html=True,
+        )
         self.assertNotContains(response, "Add another Author-Book Relationship")
         self.assertNotContains(response, 'id="id_Author_books-TOTAL_FORMS"')
 
     def test_inline_add_fk_noperm(self):
         response = self.client.get(reverse("admin:admin_inlines_holder2_add"))
         # No permissions on Inner2s, so no inline
-        self.assertNotContains(response, "<h2>Inner2s</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="inner2_set-2-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
         self.assertNotContains(response, "Add another Inner2")
         self.assertNotContains(response, 'id="id_inner2_set-TOTAL_FORMS"')
 
     def test_inline_change_m2m_noperm(self):
         response = self.client.get(self.author_change_url)
         # No change permission on books, so no inline
-        self.assertNotContains(response, "<h2>Author-book relationships</h2>")
+        self.assertNotContains(
+            response,
+            (
+                '<h2 id="Author_books-heading" class="inline-heading">'
+                "Author-book relationships</h2>"
+            ),
+            html=True,
+        )
         self.assertNotContains(response, "Add another Author-Book Relationship")
         self.assertNotContains(response, 'id="id_Author_books-TOTAL_FORMS"')
 
     def test_inline_change_fk_noperm(self):
         response = self.client.get(self.holder_change_url)
         # No permissions on Inner2s, so no inline
-        self.assertNotContains(response, "<h2>Inner2s</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="inner2_set-2-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
         self.assertNotContains(response, "Add another Inner2")
         self.assertNotContains(response, 'id="id_inner2_set-TOTAL_FORMS"')
 
@@ -959,7 +1010,14 @@ class TestInlinePermissions(TestCase):
         self.assertIs(
             response.context["inline_admin_formset"].has_delete_permission, False
         )
-        self.assertContains(response, "<h2>Author-book relationships</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="Author_books-heading" class="inline-heading">'
+                "Author-book relationships</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(
             response,
             '<input type="hidden" name="Author_books-TOTAL_FORMS" value="0" '
@@ -975,7 +1033,14 @@ class TestInlinePermissions(TestCase):
         self.user.user_permissions.add(permission)
         response = self.client.get(reverse("admin:admin_inlines_author_add"))
         # No change permission on Books, so no inline
-        self.assertNotContains(response, "<h2>Author-book relationships</h2>")
+        self.assertNotContains(
+            response,
+            (
+                '<h2 id="Author_books-heading" class="inline-heading">'
+                "Author-book relationships</h2>"
+            ),
+            html=True,
+        )
         self.assertNotContains(response, "Add another Author-Book Relationship")
         self.assertNotContains(response, 'id="id_Author_books-TOTAL_FORMS"')
 
@@ -986,7 +1051,11 @@ class TestInlinePermissions(TestCase):
         self.user.user_permissions.add(permission)
         response = self.client.get(reverse("admin:admin_inlines_holder2_add"))
         # Add permission on inner2s, so we get the inline
-        self.assertContains(response, "<h2>Inner2s</h2>")
+        self.assertContains(
+            response,
+            '<h2 id="inner2_set-2-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
         self.assertContains(response, "Add another Inner2")
         self.assertContains(
             response,
@@ -1002,7 +1071,14 @@ class TestInlinePermissions(TestCase):
         self.user.user_permissions.add(permission)
         response = self.client.get(self.author_change_url)
         # No change permission on books, so no inline
-        self.assertNotContains(response, "<h2>Author-book relationships</h2>")
+        self.assertNotContains(
+            response,
+            (
+                '<h2 id="Author_books-heading" class="inline-heading">'
+                "Author-book relationships</h2>"
+            ),
+            html=True,
+        )
         self.assertNotContains(response, "Add another Author-Book Relationship")
         self.assertNotContains(response, 'id="id_Author_books-TOTAL_FORMS"')
         self.assertNotContains(response, 'id="id_Author_books-0-DELETE"')
@@ -1026,7 +1102,14 @@ class TestInlinePermissions(TestCase):
         self.assertIs(
             response.context["inline_admin_formset"].has_delete_permission, False
         )
-        self.assertContains(response, "<h2>Author-book relationships</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="Author_books-heading" class="inline-heading">'
+                "Author-book relationships</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(
             response,
             '<input type="hidden" name="Author_books-TOTAL_FORMS" value="1" '
@@ -1059,7 +1142,14 @@ class TestInlinePermissions(TestCase):
         self.assertIs(
             response.context["inline_admin_formset"].has_delete_permission, True
         )
-        self.assertContains(response, "<h2>Author-book relationships</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="Author_books-heading" class="inline-heading">'
+                "Author-book relationships</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Author-book relationship")
         self.assertContains(
             response,
@@ -1082,7 +1172,11 @@ class TestInlinePermissions(TestCase):
         self.user.user_permissions.add(permission)
         response = self.client.get(self.holder_change_url)
         # Add permission on inner2s, so we can add but not modify existing
-        self.assertContains(response, "<h2>Inner2s</h2>")
+        self.assertContains(
+            response,
+            '<h2 id="inner2_set-2-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
         self.assertContains(response, "Add another Inner2")
         # 3 extra forms only, not the existing instance form
         self.assertContains(
@@ -1105,7 +1199,16 @@ class TestInlinePermissions(TestCase):
         self.user.user_permissions.add(permission)
         response = self.client.get(self.holder_change_url)
         # Change permission on inner2s, so we can change existing but not add new
-        self.assertContains(response, "<h2>Inner2s</h2>", count=2)
+        self.assertContains(
+            response,
+            '<h2 id="inner2_set-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
+        self.assertContains(
+            response,
+            '<h2 id="inner2_set-2-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
         # Just the one form for existing instances
         self.assertContains(
             response,
@@ -1148,7 +1251,11 @@ class TestInlinePermissions(TestCase):
         self.user.user_permissions.add(permission)
         response = self.client.get(self.holder_change_url)
         # Add/change perm, so we can add new and change existing
-        self.assertContains(response, "<h2>Inner2s</h2>")
+        self.assertContains(
+            response,
+            '<h2 id="inner2_set-2-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
         # One form for existing instance and three extra for new
         self.assertContains(
             response,
@@ -1174,7 +1281,11 @@ class TestInlinePermissions(TestCase):
         self.user.user_permissions.add(permission)
         response = self.client.get(self.holder_change_url)
         # Change/delete perm on inner2s, so we can change/delete existing
-        self.assertContains(response, "<h2>Inner2s</h2>")
+        self.assertContains(
+            response,
+            '<h2 id="inner2_set-2-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
         # One form for existing instance only, no new
         self.assertContains(
             response,
@@ -1205,7 +1316,16 @@ class TestInlinePermissions(TestCase):
         self.user.user_permissions.add(permission)
         response = self.client.get(self.holder_change_url)
         # All perms on inner2s, so we can add/change/delete
-        self.assertContains(response, "<h2>Inner2s</h2>", count=2)
+        self.assertContains(
+            response,
+            '<h2 id="inner2_set-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
+        self.assertContains(
+            response,
+            '<h2 id="inner2_set-2-heading" class="inline-heading">Inner2s</h2>',
+            html=True,
+        )
         # One form for existing instance only, three for new
         self.assertContains(
             response,
@@ -1367,22 +1487,69 @@ class TestVerboseNameInlineForms(TestDataMixin, TestCase):
         response = modeladmin.changeform_view(request)
         self.assertNotContains(response, "Add another Profile")
         # Non-verbose model.
-        self.assertContains(response, "<h2>Non-verbose childss</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="profile_set-heading" class="inline-heading">'
+                "Non-verbose childss</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Non-verbose child")
-        self.assertNotContains(response, "<h2>Profiles</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="profile_set-heading" class="inline-heading">Profiles</h2>',
+            html=True,
+        )
         # Model with verbose name.
-        self.assertContains(response, "<h2>Childs with verbose names</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="verbosenameprofile_set-heading" class="inline-heading">'
+                "Childs with verbose names</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Childs with verbose name")
-        self.assertNotContains(response, "<h2>Model with verbose name onlys</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="verbosenameprofile_set-heading" class="inline-heading">'
+            "Model with verbose name onlys</h2>",
+            html=True,
+        )
         self.assertNotContains(response, "Add another Model with verbose name only")
         # Model with verbose name plural.
-        self.assertContains(response, "<h2>Childs with verbose name plurals</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="verbosenamepluralprofile_set-heading" class="inline-heading">'
+                "Childs with verbose name plurals</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Childs with verbose name plural")
-        self.assertNotContains(response, "<h2>Model with verbose name plural only</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="verbosenamepluralprofile_set-heading" class="inline-heading">'
+            "Model with verbose name plural only</h2>",
+            html=True,
+        )
         # Model with both verbose names.
-        self.assertContains(response, "<h2>Childs with both verbose namess</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="bothverbosenameprofile_set-heading" class="inline-heading">'
+                "Childs with both verbose namess</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Childs with both verbose names")
-        self.assertNotContains(response, "<h2>Model with both - plural name</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="bothverbosenameprofile_set-heading" class="inline-heading">'
+            "Model with both - plural name</h2>",
+            html=True,
+        )
         self.assertNotContains(response, "Add another Model with both - name")
 
     def test_verbose_name_plural_inline(self):
@@ -1415,21 +1582,68 @@ class TestVerboseNameInlineForms(TestDataMixin, TestCase):
         request.user = self.superuser
         response = modeladmin.changeform_view(request)
         # Non-verbose model.
-        self.assertContains(response, "<h2>Non-verbose childs</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="profile_set-heading" class="inline-heading">'
+                "Non-verbose childs</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Profile")
-        self.assertNotContains(response, "<h2>Profiles</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="profile_set-heading" class="inline-heading">Profiles</h2>',
+            html=True,
+        )
         # Model with verbose name.
-        self.assertContains(response, "<h2>Childs with verbose name</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="verbosenameprofile_set-heading" class="inline-heading">'
+                "Childs with verbose name</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Model with verbose name only")
-        self.assertNotContains(response, "<h2>Model with verbose name onlys</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="verbosenameprofile_set-heading" class="inline-heading">'
+            "Model with verbose name onlys</h2>",
+            html=True,
+        )
         # Model with verbose name plural.
-        self.assertContains(response, "<h2>Childs with verbose name plural</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="verbosenamepluralprofile_set-heading" class="inline-heading">'
+                "Childs with verbose name plural</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Profile")
-        self.assertNotContains(response, "<h2>Model with verbose name plural only</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="verbosenamepluralprofile_set-heading" class="inline-heading">'
+            "Model with verbose name plural only</h2>",
+            html=True,
+        )
         # Model with both verbose names.
-        self.assertContains(response, "<h2>Childs with both verbose names</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="bothverbosenameprofile_set-heading" class="inline-heading">'
+                "Childs with both verbose names</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Model with both - name")
-        self.assertNotContains(response, "<h2>Model with both - plural name</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="bothverbosenameprofile_set-heading" class="inline-heading">'
+            "Model with both - plural name</h2>",
+            html=True,
+        )
 
     def test_both_verbose_names_inline(self):
         class NonVerboseProfileInline(TabularInline):
@@ -1466,31 +1680,149 @@ class TestVerboseNameInlineForms(TestDataMixin, TestCase):
         response = modeladmin.changeform_view(request)
         self.assertNotContains(response, "Add another Profile")
         # Non-verbose model.
-        self.assertContains(response, "<h2>Non-verbose childs - plural name</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="profile_set-heading" class="inline-heading">'
+                "Non-verbose childs - plural name</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Non-verbose childs - name")
-        self.assertNotContains(response, "<h2>Profiles</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="profile_set-heading" class="inline-heading">Profiles</h2>',
+            html=True,
+        )
         # Model with verbose name.
-        self.assertContains(response, "<h2>Childs with verbose name - plural name</h2>")
+        self.assertContains(
+            response,
+            (
+                '<h2 id="verbosenameprofile_set-heading" class="inline-heading">'
+                "Childs with verbose name - plural name</h2>"
+            ),
+            html=True,
+        )
         self.assertContains(response, "Add another Childs with verbose name - name")
-        self.assertNotContains(response, "<h2>Model with verbose name onlys</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="verbosenameprofile_set-heading" class="inline-heading">'
+            "Model with verbose name onlys</h2>",
+            html=True,
+        )
         # Model with verbose name plural.
         self.assertContains(
             response,
-            "<h2>Childs with verbose name plural - plural name</h2>",
+            (
+                '<h2 id="verbosenamepluralprofile_set-heading" class="inline-heading">'
+                "Childs with verbose name plural - plural name</h2>"
+            ),
+            html=True,
         )
         self.assertContains(
             response,
             "Add another Childs with verbose name plural - name",
         )
-        self.assertNotContains(response, "<h2>Model with verbose name plural only</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="verbosenamepluralprofile_set-heading" class="inline-heading">'
+            "Model with verbose name plural only</h2>",
+            html=True,
+        )
         # Model with both verbose names.
-        self.assertContains(response, "<h2>Childs with both - plural name</h2>")
+        self.assertContains(
+            response,
+            '<h2 id="bothverbosenameprofile_set-heading" class="inline-heading">'
+            "Childs with both - plural name</h2>",
+            html=True,
+        )
         self.assertContains(response, "Add another Childs with both - name")
-        self.assertNotContains(response, "<h2>Model with both - plural name</h2>")
+        self.assertNotContains(
+            response,
+            '<h2 id="bothverbosenameprofile_set-heading" class="inline-heading">'
+            "Model with both - plural name</h2>",
+            html=True,
+        )
         self.assertNotContains(response, "Add another Model with both - name")
 
 
 @override_settings(ROOT_URLCONF="admin_inlines.urls")
+class TestInlineWithFieldsets(TestDataMixin, TestCase):
+    def setUp(self):
+        self.client.force_login(self.superuser)
+
+    def test_inline_headings(self):
+        response = self.client.get(reverse("admin:admin_inlines_photographer_add"))
+        # Page main title.
+        self.assertContains(response, "<h1>Add photographer</h1>", html=True)
+
+        # Headings for the toplevel fieldsets. The first one has no name.
+        self.assertContains(response, '<fieldset class="module aligned ">')
+        # The second and third have the same "Advanced options" name, but the
+        # second one has the "collapse" class.
+        for x, classes in ((1, ""), (2, "collapse")):
+            heading_id = f"fieldset-0-advanced-options-{x}-heading"
+            with self.subTest(heading_id=heading_id):
+                self.assertContains(
+                    response,
+                    f'<fieldset class="module aligned {classes}" '
+                    f'aria-labelledby="{heading_id}">',
+                )
+                self.assertContains(
+                    response,
+                    f'<h2 id="{heading_id}" class="fieldset-heading">'
+                    "Advanced options</h2>",
+                )
+                self.assertContains(response, f'id="{heading_id}"', count=1)
+
+        # Headings and subheadings for all the inlines.
+        for inline_admin_formset in response.context["inline_admin_formsets"]:
+            prefix = inline_admin_formset.formset.prefix
+            heading_id = f"{prefix}-heading"
+            formset_heading = (
+                f'<h2 id="{heading_id}" class="inline-heading">Photos</h2>'
+            )
+            self.assertContains(response, formset_heading, html=True)
+            self.assertContains(response, f'id="{heading_id}"', count=1)
+
+            # If this is a TabularInline, do not make further asserts since
+            # fieldsets are not shown as such in this table layout.
+            if "tabular" in inline_admin_formset.opts.template:
+                continue
+
+            # Headings for every formset (the amount depends on `extra`).
+            for y, inline_admin_form in enumerate(inline_admin_formset):
+                y_plus_one = y + 1
+                form_heading = (
+                    f'<h3><b>Photo:</b> <span class="inline_label">#{y_plus_one}</span>'
+                    "</h3>"
+                )
+                self.assertContains(response, form_heading, html=True)
+
+                # Every fieldset defined for an inline's form.
+                for z, fieldset in enumerate(inline_admin_form):
+                    if fieldset.name:
+                        heading_id = f"{prefix}-{y}-details-{z}-heading"
+                        self.assertContains(
+                            response,
+                            f'<fieldset class="module aligned {fieldset.classes}" '
+                            f'aria-labelledby="{heading_id}">',
+                        )
+                        fieldset_heading = (
+                            f'<h4 id="{heading_id}" class="fieldset-heading">'
+                            f"Details</h4>"
+                        )
+                        self.assertContains(response, fieldset_heading)
+                        self.assertContains(response, f'id="{heading_id}"', count=1)
+
+                    else:
+                        fieldset_html = (
+                            f'<fieldset class="module aligned {fieldset.classes}">'
+                        )
+                        self.assertContains(response, fieldset_html)
+
+
+@override_settings(ROOT_URLCONF="admin_inlines.urls")
 class SeleniumTests(AdminSeleniumTestCase):
     available_apps = ["admin_inlines"] + AdminSeleniumTestCase.available_apps