diff --git a/packages/core-app-api/src/app/AppRouter.test.tsx b/packages/core-app-api/src/app/AppRouter.test.tsx
new file mode 100644
index 0000000000..75f28a6bfe
--- /dev/null
+++ b/packages/core-app-api/src/app/AppRouter.test.tsx
@@ -0,0 +1,120 @@
+/*
+ * Copyright 2022 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 React from 'react';
+import {
+  AppComponents,
+  configApiRef,
+  IdentityApi,
+  identityApiRef,
+  SignInPageProps,
+  useApi,
+} from '@backstage/core-plugin-api';
+import { InternalAppContext } from './InternalAppContext';
+import { MemoryRouter } from 'react-router-dom';
+import { AppIdentityProxy } from '../apis/implementations/IdentityApi/AppIdentityProxy';
+import { render, screen } from '@testing-library/react';
+import { AppRouter } from './AppRouter';
+import useAsync from 'react-use/lib/useAsync';
+import { AppContextProvider } from './AppContext';
+import { TestApiProvider } from '@backstage/test-utils';
+import { ConfigReader } from '@backstage/config';
+
+function UserRefDisplay() {
+  const identityApi = useApi(identityApiRef);
+  const { value } = useAsync(() => identityApi.getBackstageIdentity());
+  return <div>ref: {value?.userEntityRef}</div>;
+}
+
+describe('AppRouter', () => {
+  const mockComponents = {
+    Router: MemoryRouter,
+  } as AppComponents;
+
+  it('should fall back to guest if there is no sign-in page', async () => {
+    const appIdentityProxy = new AppIdentityProxy();
+
+    render(
+      <TestApiProvider
+        apis={[
+          [identityApiRef, appIdentityProxy],
+          [configApiRef, new ConfigReader({})],
+        ]}
+      >
+        <InternalAppContext.Provider
+          value={{ routeObjects: [], appIdentityProxy }}
+        >
+          <AppContextProvider
+            appContext={{ getComponents: () => mockComponents } as any}
+          >
+            <AppRouter>
+              <UserRefDisplay />
+            </AppRouter>
+          </AppContextProvider>
+        </InternalAppContext.Provider>
+        ,
+      </TestApiProvider>,
+    );
+
+    await expect(
+      screen.findByText('ref: user:default/guest'),
+    ).resolves.toBeInTheDocument();
+  });
+
+  it('should use the result from the sign-in page', async () => {
+    const appIdentityProxy = new AppIdentityProxy();
+
+    const SignInPage = (props: SignInPageProps) => {
+      props.onSignInSuccess({
+        getBackstageIdentity: async () => ({
+          type: 'user',
+          userEntityRef: 'user:default/test',
+          ownershipEntityRefs: ['user:default/test'],
+        }),
+      } as IdentityApi);
+      return null;
+    };
+
+    render(
+      <TestApiProvider
+        apis={[
+          [identityApiRef, appIdentityProxy],
+          [configApiRef, new ConfigReader({})],
+        ]}
+      >
+        <InternalAppContext.Provider
+          value={{ routeObjects: [], appIdentityProxy }}
+        >
+          <AppContextProvider
+            appContext={
+              {
+                getComponents: () => ({ ...mockComponents, SignInPage }),
+              } as any
+            }
+          >
+            <AppRouter>
+              <UserRefDisplay />
+            </AppRouter>
+          </AppContextProvider>
+        </InternalAppContext.Provider>
+      </TestApiProvider>,
+    );
+
+    await expect(
+      screen.findByText('ref: user:default/test'),
+    ).resolves.toBeInTheDocument();
+  });
+});