diff --git a/.changeset/fluffy-cities-sip.md b/.changeset/fluffy-cities-sip.md
new file mode 100644
index 0000000000..1f82540e38
--- /dev/null
+++ b/.changeset/fluffy-cities-sip.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-app': patch
+---
+
+Fixed an issue that caused the `NotFound` page to not render correctly when a Page was mounted at `/`.
diff --git a/.changeset/real-seals-dress.md b/.changeset/real-seals-dress.md
new file mode 100644
index 0000000000..7f490d3ce9
--- /dev/null
+++ b/.changeset/real-seals-dress.md
@@ -0,0 +1,5 @@
+---
+'@backstage/frontend-test-utils': minor
+---
+
+**BREAKING**: Removed the `extensions` option from `renderInTestApp`. If you need to pass extensions to the test app, use the new `renderTestApp` utility instead.
diff --git a/packages/core-compat-api/src/collectLegacyRoutes.test.tsx b/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
index fe4166016e..c5138dac3d 100644
--- a/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
+++ b/packages/core-compat-api/src/collectLegacyRoutes.test.tsx
@@ -39,7 +39,7 @@ import {
   useApp,
 } from '@backstage/core-plugin-api';
 import { screen } from '@testing-library/react';
-import { renderInTestApp } from '@backstage/frontend-test-utils';
+import { renderTestApp } from '@backstage/frontend-test-utils';
 
 const exampleApiRef = createApiRef<string>({
   id: 'plugin.example.service',
@@ -304,7 +304,7 @@ describe('collectLegacyRoutes', () => {
       </FlatRoutes>,
     );
 
-    renderInTestApp(<div />, { features });
+    renderTestApp({ features });
 
     await expect(
       screen.findByText('plugins: app, test'),
diff --git a/packages/core-compat-api/src/convertLegacyApp.test.tsx b/packages/core-compat-api/src/convertLegacyApp.test.tsx
index 7bbe13867c..1cb2b757e3 100644
--- a/packages/core-compat-api/src/convertLegacyApp.test.tsx
+++ b/packages/core-compat-api/src/convertLegacyApp.test.tsx
@@ -27,7 +27,7 @@ import {
   createRouteRef,
 } from '@backstage/core-plugin-api';
 import { EntityLayout, EntitySwitch, isKind } from '@backstage/plugin-catalog';
-import { renderInTestApp } from '@backstage/frontend-test-utils';
+import { renderTestApp } from '@backstage/frontend-test-utils';
 import { default as catalogPlugin } from '@backstage/plugin-catalog/alpha';
 import { catalogApiRef } from '@backstage/plugin-catalog-react';
 import { catalogApiMock } from '@backstage/plugin-catalog-react/testUtils';
@@ -263,7 +263,7 @@ describe('convertLegacyApp', () => {
     });
 
     // Overview
-    const renderOverviewTest = await renderInTestApp(<div />, {
+    const renderOverviewTest = await renderTestApp({
       features: [catalogOverride, ...converted],
       initialRouteEntries: ['/catalog/default/test/x'],
     });
@@ -272,7 +272,7 @@ describe('convertLegacyApp', () => {
     ).resolves.toBeInTheDocument();
     renderOverviewTest.unmount();
 
-    const renderOverviewOther = await renderInTestApp(<div />, {
+    const renderOverviewOther = await renderTestApp({
       features: [catalogOverride, ...converted],
       initialRouteEntries: ['/catalog/default/other/x'],
     });
@@ -282,7 +282,7 @@ describe('convertLegacyApp', () => {
     renderOverviewOther.unmount();
 
     // Foo tab
-    const renderFooTest = await renderInTestApp(<div />, {
+    const renderFooTest = await renderTestApp({
       features: [catalogOverride, ...converted],
       initialRouteEntries: ['/catalog/default/test/x/foo'],
     });
@@ -291,7 +291,7 @@ describe('convertLegacyApp', () => {
     ).resolves.toBeInTheDocument();
     renderFooTest.unmount();
 
-    const renderFooOther = await renderInTestApp(<div />, {
+    const renderFooOther = await renderTestApp({
       features: [catalogOverride, ...converted],
       initialRouteEntries: ['/catalog/default/other/x/foo'],
     });
@@ -301,7 +301,7 @@ describe('convertLegacyApp', () => {
     renderFooOther.unmount();
 
     // Bar tab
-    const renderBarTest = await renderInTestApp(<div />, {
+    const renderBarTest = await renderTestApp({
       features: [catalogOverride, ...converted],
       initialRouteEntries: ['/catalog/default/test/x/bar'],
     });
@@ -310,7 +310,7 @@ describe('convertLegacyApp', () => {
     ).resolves.toBeInTheDocument();
     renderBarTest.unmount();
 
-    const renderBarOther = await renderInTestApp(<div />, {
+    const renderBarOther = await renderTestApp({
       features: [catalogOverride, ...converted],
       initialRouteEntries: ['/catalog/default/other/x/bar'],
     });
diff --git a/packages/frontend-plugin-api/src/blueprints/AppRootWrapperBlueprint.test.tsx b/packages/frontend-plugin-api/src/blueprints/AppRootWrapperBlueprint.test.tsx
index b4ad8ed2d2..0f26af3243 100644
--- a/packages/frontend-plugin-api/src/blueprints/AppRootWrapperBlueprint.test.tsx
+++ b/packages/frontend-plugin-api/src/blueprints/AppRootWrapperBlueprint.test.tsx
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
+import { Fragment } from 'react';
 import { AppRootWrapperBlueprint } from './AppRootWrapperBlueprint';
 import { screen, waitFor } from '@testing-library/react';
 import {
@@ -21,7 +21,7 @@ import {
   createExtension,
   createExtensionInput,
 } from '../wiring';
-import { renderInTestApp } from '@backstage/frontend-test-utils';
+import { renderTestApp } from '@backstage/frontend-test-utils';
 
 describe('AppRootWrapperBlueprint', () => {
   it('should return an extension with sensible defaults', () => {
@@ -63,7 +63,7 @@ describe('AppRootWrapperBlueprint', () => {
       },
     });
 
-    renderInTestApp(<div />, { extensions: [extension] });
+    renderTestApp({ extensions: [extension] });
 
     await waitFor(() => expect(screen.getByText('Hello')).toBeInTheDocument());
   });
@@ -83,16 +83,18 @@ describe('AppRootWrapperBlueprint', () => {
           component: ({ children }) => (
             <div data-testid={`${config.name}-${inputs.children.length}`}>
               {children}
-              {inputs.children.flatMap(c =>
-                c.get(coreExtensionData.reactElement),
-              )}
+              {inputs.children.flatMap((c, index) => (
+                <Fragment key={index}>
+                  {c.get(coreExtensionData.reactElement)}
+                </Fragment>
+              ))}
             </div>
           ),
         });
       },
     });
 
-    renderInTestApp(<div />, {
+    renderTestApp({
       extensions: [
         extension,
         createExtension({
diff --git a/packages/frontend-plugin-api/src/blueprints/SwappableComponentBlueprint.test.tsx b/packages/frontend-plugin-api/src/blueprints/SwappableComponentBlueprint.test.tsx
index fae4bf7ebf..63436308ed 100644
--- a/packages/frontend-plugin-api/src/blueprints/SwappableComponentBlueprint.test.tsx
+++ b/packages/frontend-plugin-api/src/blueprints/SwappableComponentBlueprint.test.tsx
@@ -13,11 +13,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import { renderInTestApp } from '@backstage/frontend-test-utils';
+import { renderTestApp } from '@backstage/frontend-test-utils';
 import { createSwappableComponent } from '../components';
 import { SwappableComponentBlueprint } from './SwappableComponentBlueprint';
 import { PageBlueprint } from './PageBlueprint';
-import { waitFor, screen } from '@testing-library/react';
+import { screen } from '@testing-library/react';
 
 describe('SwappableComponentBlueprint', () => {
   it('should allow defining a component override for a component ref', () => {
@@ -48,21 +48,19 @@ describe('SwappableComponentBlueprint', () => {
       loader: () => (props: { hello: string }) => <div>{props.hello}</div>,
     });
 
-    renderInTestApp(<div />, {
+    renderTestApp({
       extensions: [
         PageBlueprint.make({
           params: define =>
             define({
-              // todo(blam): there's a bug that this path cannot be `/`?
-              path: '/test',
+              path: '/',
               loader: async () => <TestComponent hello="test!" />,
             }),
         }),
       ],
-      initialRouteEntries: ['/test'],
     });
 
-    await waitFor(() => expect(screen.getByText('test!')).toBeInTheDocument());
+    await expect(screen.findByText('test!')).resolves.toBeInTheDocument();
   });
 
   it('should render a component ref without a default implementation', async () => {
@@ -70,22 +68,21 @@ describe('SwappableComponentBlueprint', () => {
       id: 'test.component',
     });
 
-    renderInTestApp(<div />, {
+    renderTestApp({
       extensions: [
         PageBlueprint.make({
           params: define =>
             define({
-              path: '/test',
+              path: '/',
               loader: async () => <TestComponent />,
             }),
         }),
       ],
-      initialRouteEntries: ['/test'],
     });
 
-    await waitFor(() =>
-      expect(screen.getByTestId('test.component')).toBeInTheDocument(),
-    );
+    await expect(
+      screen.findByTestId('test.component'),
+    ).resolves.toBeInTheDocument();
   });
 
   it('should render a component ref with an async loader implementation', async () => {
@@ -95,21 +92,20 @@ describe('SwappableComponentBlueprint', () => {
         <div>{props.hello}</div>,
     });
 
-    renderInTestApp(<div />, {
+    renderTestApp({
       extensions: [
         PageBlueprint.make({
           params: define =>
             define({
               // todo(blam): there's a bug that this path cannot be `/`?
-              path: '/test',
+              path: '/',
               loader: async () => <TestComponent hello="test!" />,
             }),
         }),
       ],
-      initialRouteEntries: ['/test'],
     });
 
-    await waitFor(() => expect(screen.getByText('test!')).toBeInTheDocument());
+    await expect(screen.findByText('test!')).resolves.toBeInTheDocument();
   });
 
   it('should render a component ref with an async loader implementation and prop transform', async () => {
@@ -120,22 +116,18 @@ describe('SwappableComponentBlueprint', () => {
       transformProps: ({ hello }) => ({ hello: `tr ${hello}` }),
     });
 
-    renderInTestApp(<div />, {
+    renderTestApp({
       extensions: [
         PageBlueprint.make({
           params: define =>
             define({
-              // todo(blam): there's a bug that this path cannot be `/`?
-              path: '/test',
+              path: '/',
               loader: async () => <TestComponent hello="test!" />,
             }),
         }),
       ],
-      initialRouteEntries: ['/test'],
     });
 
-    await waitFor(() =>
-      expect(screen.getByText('tr test!')).toBeInTheDocument(),
-    );
+    await expect(screen.findByText('tr test!')).resolves.toBeInTheDocument();
   });
 });
diff --git a/packages/frontend-test-utils/report.api.md b/packages/frontend-test-utils/report.api.md
index db31c082ea..b99cf843d4 100644
--- a/packages/frontend-test-utils/report.api.md
+++ b/packages/frontend-test-utils/report.api.md
@@ -29,6 +29,7 @@ import { RouteRef } from '@backstage/frontend-plugin-api';
 import { TestApiProvider } from '@backstage/test-utils';
 import { TestApiProviderProps } from '@backstage/test-utils';
 import { TestApiRegistry } from '@backstage/test-utils';
+import { testingLibraryDomTypesQueries } from '@testing-library/dom/types/queries';
 import { withLogCollector } from '@backstage/test-utils';
 
 export { ApiMock };
@@ -119,6 +120,19 @@ export function renderInTestApp(
   options?: TestAppOptions,
 ): RenderResult;
 
+// @public
+export function renderTestApp(
+  options: RenderTestAppOptions,
+): RenderResult<testingLibraryDomTypesQueries, HTMLElement, HTMLElement>;
+
+// @public
+export type RenderTestAppOptions = {
+  config?: JsonObject;
+  extensions?: ExtensionDefinition<any>[];
+  features?: FrontendFeature[];
+  initialRouteEntries?: string[];
+};
+
 export { TestApiProvider };
 
 export { TestApiProviderProps };
@@ -131,7 +145,6 @@ export type TestAppOptions = {
     [path: string]: RouteRef;
   };
   config?: JsonObject;
-  extensions?: ExtensionDefinition<any>[];
   features?: FrontendFeature[];
   initialRouteEntries?: string[];
 };
diff --git a/packages/frontend-test-utils/src/app/index.ts b/packages/frontend-test-utils/src/app/index.ts
index 6c6ef26e4c..9db67dbb49 100644
--- a/packages/frontend-test-utils/src/app/index.ts
+++ b/packages/frontend-test-utils/src/app/index.ts
@@ -21,3 +21,4 @@ export {
 } from './createExtensionTester';
 
 export { renderInTestApp, type TestAppOptions } from './renderInTestApp';
+export { renderTestApp, type RenderTestAppOptions } from './renderTestApp';
diff --git a/packages/frontend-test-utils/src/app/renderInTestApp.tsx b/packages/frontend-test-utils/src/app/renderInTestApp.tsx
index 80818509da..747229e8d6 100644
--- a/packages/frontend-test-utils/src/app/renderInTestApp.tsx
+++ b/packages/frontend-test-utils/src/app/renderInTestApp.tsx
@@ -67,11 +67,6 @@ export type TestAppOptions = {
    */
   config?: JsonObject;
 
-  /**
-   * Additional extensions to add to the test app.
-   */
-  extensions?: ExtensionDefinition<any>[];
-
   /**
    * Additional features to add to the test app.
    */
@@ -107,6 +102,12 @@ const appPluginOverride = appPlugin.withOverrides({
     appPlugin.getExtension('sign-in-page:app').override({
       disabled: true,
     }),
+    appPlugin.getExtension('app/layout').override({
+      disabled: true,
+    }),
+    appPlugin.getExtension('app/routes').override({
+      disabled: true,
+    }),
     appPlugin.getExtension('app/nav').override({
       output: [coreExtensionData.reactElement],
       factory(_originalFactory, { inputs }) {
@@ -147,13 +148,10 @@ export function renderInTestApp(
 ): RenderResult {
   const extensions: Array<ExtensionDefinition> = [
     createExtension({
-      attachTo: { id: 'app/routes', input: 'routes' },
-      output: [coreExtensionData.reactElement, coreExtensionData.routePath],
+      attachTo: { id: 'app/root', input: 'children' },
+      output: [coreExtensionData.reactElement],
       factory: () => {
-        return [
-          coreExtensionData.reactElement(element),
-          coreExtensionData.routePath('/'),
-        ];
+        return [coreExtensionData.reactElement(element)];
       },
     }),
     RouterBlueprint.make({
@@ -190,10 +188,6 @@ export function renderInTestApp(
     }
   }
 
-  if (options?.extensions) {
-    extensions.push(...options.extensions);
-  }
-
   const features: FrontendFeature[] = [
     createFrontendPlugin({
       pluginId: 'test',
diff --git a/packages/frontend-test-utils/src/app/renderTestApp.tsx b/packages/frontend-test-utils/src/app/renderTestApp.tsx
new file mode 100644
index 0000000000..e8d90cadd6
--- /dev/null
+++ b/packages/frontend-test-utils/src/app/renderTestApp.tsx
@@ -0,0 +1,115 @@
+/*
+ * Copyright 2025 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { createSpecializedApp } from '@backstage/frontend-app-api';
+import {
+  coreExtensionData,
+  createFrontendPlugin,
+  ExtensionDefinition,
+  FrontendFeature,
+  RouterBlueprint,
+} from '@backstage/frontend-plugin-api';
+import { render } from '@testing-library/react';
+import appPlugin from '@backstage/plugin-app';
+import { JsonObject } from '@backstage/types';
+import { ConfigReader } from '@backstage/config';
+import { MemoryRouter } from 'react-router-dom';
+
+const DEFAULT_MOCK_CONFIG = {
+  app: { baseUrl: 'http://localhost:3000' },
+  backend: { baseUrl: 'http://localhost:7007' },
+};
+
+/**
+ * Options for `renderTestApp`.
+ *
+ * @public
+ */
+export type RenderTestAppOptions = {
+  /**
+   * Additional configuration passed to the app when rendering elements inside it.
+   */
+  config?: JsonObject;
+  /**
+   * Additional extensions to add to the test app.
+   */
+  extensions?: ExtensionDefinition<any>[];
+
+  /**
+   * Additional features to add to the test app.
+   */
+  features?: FrontendFeature[];
+
+  /**
+   * Initial route entries to use for the router.
+   */
+  initialRouteEntries?: string[];
+};
+
+const appPluginOverride = appPlugin.withOverrides({
+  extensions: [
+    appPlugin.getExtension('sign-in-page:app').override({
+      disabled: true,
+    }),
+  ],
+});
+
+/**
+ * Renders the provided extensions inside a Backstage app, returning the same
+ * utilities as `@testing-library/react` `render` function.
+ *
+ * @public
+ */
+export function renderTestApp(options: RenderTestAppOptions) {
+  const extensions = [
+    RouterBlueprint.make({
+      params: {
+        component: ({ children }) => (
+          <MemoryRouter initialEntries={options.initialRouteEntries}>
+            {children}
+          </MemoryRouter>
+        ),
+      },
+    }),
+    ...(options.extensions ?? []),
+  ];
+
+  const features: FrontendFeature[] = [
+    createFrontendPlugin({
+      pluginId: 'test',
+      extensions,
+    }),
+    appPluginOverride,
+  ];
+
+  if (options.features) {
+    features.push(...options.features);
+  }
+
+  const app = createSpecializedApp({
+    features,
+    config: ConfigReader.fromConfigs([
+      {
+        context: 'render-config',
+        data: options?.config ?? DEFAULT_MOCK_CONFIG,
+      },
+    ]),
+  });
+
+  return render(
+    app.tree.root.instance!.getData(coreExtensionData.reactElement),
+  );
+}
diff --git a/plugins/app/src/apis/SwappableComponentsApi/DefaultSwappableComponentsApi.test.tsx b/plugins/app/src/apis/SwappableComponentsApi/DefaultSwappableComponentsApi.test.tsx
index 07ef891926..bdd81f338c 100644
--- a/plugins/app/src/apis/SwappableComponentsApi/DefaultSwappableComponentsApi.test.tsx
+++ b/plugins/app/src/apis/SwappableComponentsApi/DefaultSwappableComponentsApi.test.tsx
@@ -16,6 +16,7 @@
 
 import {
   ApiBlueprint,
+  AppRootElementBlueprint,
   createExtensionInput,
   createFrontendModule,
   createSwappableComponent,
@@ -24,7 +25,7 @@ import {
 } from '@backstage/frontend-plugin-api';
 import { DefaultSwappableComponentsApi } from './DefaultSwappableComponentsApi';
 import { render, screen } from '@testing-library/react';
-import { renderInTestApp } from '@backstage/frontend-test-utils';
+import { renderInTestApp, renderTestApp } from '@backstage/frontend-test-utils';
 
 const { ref: testRefA } = createSwappableComponent({ id: 'test.a' });
 const { ref: testRefB1 } = createSwappableComponent({ id: 'test.b' });
@@ -149,8 +150,17 @@ describe('DefaultSwappableComponentsApi', () => {
           id: 'test.mock',
         });
 
-        renderInTestApp(<MockComponent />, {
-          extensions: [api],
+        renderTestApp({
+          extensions: [
+            AppRootElementBlueprint.make({
+              name: 'derp',
+              params: define =>
+                define({
+                  element: <MockComponent />,
+                }),
+            }),
+            api,
+          ],
         });
 
         await expect(
@@ -164,8 +174,17 @@ describe('DefaultSwappableComponentsApi', () => {
           loader: () => () => <div>test.mock</div>,
         });
 
-        renderInTestApp(<MockComponent />, {
-          extensions: [api],
+        renderTestApp({
+          extensions: [
+            AppRootElementBlueprint.make({
+              name: 'derp',
+              params: define =>
+                define({
+                  element: <MockComponent />,
+                }),
+            }),
+            api,
+          ],
         });
 
         await expect(
@@ -179,8 +198,17 @@ describe('DefaultSwappableComponentsApi', () => {
           loader: async () => () => <div>test.mock</div>,
         });
 
-        renderInTestApp(<MockComponent />, {
-          extensions: [api],
+        renderTestApp({
+          extensions: [
+            AppRootElementBlueprint.make({
+              name: 'derp',
+              params: define =>
+                define({
+                  element: <MockComponent />,
+                }),
+            }),
+            api,
+          ],
         });
 
         await expect(
@@ -202,8 +230,17 @@ describe('DefaultSwappableComponentsApi', () => {
             }),
         });
 
-        renderInTestApp(<MockComponent />, {
-          extensions: [api],
+        renderTestApp({
+          extensions: [
+            AppRootElementBlueprint.make({
+              name: 'derp',
+              params: define =>
+                define({
+                  element: <MockComponent />,
+                }),
+            }),
+            api,
+          ],
           features: [
             createFrontendModule({
               pluginId: 'app',
@@ -231,8 +268,17 @@ describe('DefaultSwappableComponentsApi', () => {
             }),
         });
 
-        renderInTestApp(<MockComponent />, {
-          extensions: [api],
+        renderTestApp({
+          extensions: [
+            AppRootElementBlueprint.make({
+              name: 'derp',
+              params: define =>
+                define({
+                  element: <MockComponent />,
+                }),
+            }),
+            api,
+          ],
           features: [
             createFrontendModule({
               pluginId: 'app',
@@ -264,8 +310,17 @@ describe('DefaultSwappableComponentsApi', () => {
             }),
         });
 
-        renderInTestApp(<MockComponent external="test" />, {
-          extensions: [api],
+        renderTestApp({
+          extensions: [
+            AppRootElementBlueprint.make({
+              name: 'derp',
+              params: define =>
+                define({
+                  element: <MockComponent external="test" />,
+                }),
+            }),
+            api,
+          ],
           features: [
             createFrontendModule({
               pluginId: 'app',
diff --git a/plugins/app/src/extensions/AppRoutes.tsx b/plugins/app/src/extensions/AppRoutes.tsx
index 5cc3c3f4b8..ddd7962004 100644
--- a/plugins/app/src/extensions/AppRoutes.tsx
+++ b/plugins/app/src/extensions/AppRoutes.tsx
@@ -36,12 +36,18 @@ export const AppRoutes = createExtension({
   factory({ inputs }) {
     const Routes = () => {
       const element = useRoutes([
-        ...inputs.routes.map(route => ({
-          path: `${route
-            .get(coreExtensionData.routePath)
-            .replace(/\/$/, '')}/*`,
-          element: route.get(coreExtensionData.reactElement),
-        })),
+        ...inputs.routes.map(route => {
+          const routePath = route.get(coreExtensionData.routePath);
+
+          return {
+            path:
+              routePath === '/'
+                ? routePath
+                : `${routePath.replace(/\/$/, '')}/*`,
+
+            element: route.get(coreExtensionData.reactElement),
+          };
+        }),
         {
           path: '*',
           element: <NotFoundErrorPage />,
diff --git a/plugins/app/src/extensions/DialogDisplay.test.tsx b/plugins/app/src/extensions/DialogDisplay.test.tsx
index 8f7eb4e857..dbad551fcb 100644
--- a/plugins/app/src/extensions/DialogDisplay.test.tsx
+++ b/plugins/app/src/extensions/DialogDisplay.test.tsx
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { renderInTestApp } from '@backstage/frontend-test-utils';
+import { renderTestApp } from '@backstage/frontend-test-utils';
 import { act, useEffect } from 'react';
 import {
   AppRootElementBlueprint,
@@ -29,7 +29,7 @@ async function withDialogApi<T>(
   callback: (dialogApi: DialogApi) => Promise<T>,
 ) {
   const deferred = createDeferred<DialogApi>();
-  await renderInTestApp(<div />, {
+  await renderTestApp({
     extensions: [
       AppRootElementBlueprint.makeWithOverrides({
         name: 'derp',