diff --git a/packages/core-compat-api/src/convertLegacyApp.test.tsx b/packages/core-compat-api/src/convertLegacyApp.test.tsx
new file mode 100644
index 0000000000..0f1f6145c9
--- /dev/null
+++ b/packages/core-compat-api/src/convertLegacyApp.test.tsx
@@ -0,0 +1,129 @@
+/*
+ * Copyright 2023 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 { AppRouter, FlatRoutes } from '@backstage/core-app-api';
+import { PuppetDbPage } from '@backstage/plugin-puppetdb';
+import { StackstormPage } from '@backstage/plugin-stackstorm';
+import { ScoreBoardPage } from '@oriflame/backstage-plugin-score-card';
+import React, { ReactNode } from 'react';
+import { Route } from 'react-router-dom';
+import { convertLegacyApp } from './convertLegacyApp';
+
+const Root = ({ children }: { children: ReactNode }) => <>{children}</>;
+
+describe('convertLegacyApp', () => {
+  it('should find and extract root and routes', () => {
+    const collected = convertLegacyApp(
+      <>
+        <div />
+        <span />
+        <AppRouter>
+          <div />
+          <Root>
+            <FlatRoutes>
+              <Route path="/score-board" element={<ScoreBoardPage />} />
+              <Route path="/stackstorm" element={<StackstormPage />} />
+              <Route path="/puppetdb" element={<PuppetDbPage />} />
+              <Route path="/puppetdb" element={<PuppetDbPage />} />
+            </FlatRoutes>
+          </Root>
+        </AppRouter>
+      </>,
+    );
+
+    expect(
+      collected.map((p: any /* TODO */) => ({
+        id: p.id,
+        extensions: p.extensions.map((e: any) => ({
+          id: e.id,
+          attachTo: e.attachTo,
+          disabled: e.disabled,
+          defaultConfig: e.configSchema?.parse({}),
+        })),
+      })),
+    ).toEqual([
+      {
+        id: 'score-card',
+        extensions: [
+          {
+            id: 'plugin.score-card.page',
+            attachTo: { id: 'core.routes', input: 'routes' },
+            disabled: false,
+            defaultConfig: { path: 'score-board' },
+          },
+          {
+            id: 'apis.plugin.scoringdata.service',
+            attachTo: { id: 'core', input: 'apis' },
+            disabled: false,
+          },
+        ],
+      },
+      {
+        id: 'stackstorm',
+        extensions: [
+          {
+            id: 'plugin.stackstorm.page',
+            attachTo: { id: 'core.routes', input: 'routes' },
+            disabled: false,
+            defaultConfig: { path: 'stackstorm' },
+          },
+          {
+            id: 'apis.plugin.stackstorm.service',
+            attachTo: { id: 'core', input: 'apis' },
+            disabled: false,
+          },
+        ],
+      },
+      {
+        id: 'puppetDb',
+        extensions: [
+          {
+            id: 'plugin.puppetDb.page',
+            attachTo: { id: 'core.routes', input: 'routes' },
+            disabled: false,
+            defaultConfig: { path: 'puppetdb' },
+          },
+          {
+            id: 'plugin.puppetDb.page2',
+            attachTo: { id: 'core.routes', input: 'routes' },
+            disabled: false,
+            defaultConfig: { path: 'puppetdb' },
+          },
+          {
+            id: 'apis.plugin.puppetdb.service',
+            attachTo: { id: 'core', input: 'apis' },
+            disabled: false,
+          },
+        ],
+      },
+      {
+        id: undefined,
+        extensions: [
+          {
+            id: 'core.layout',
+            attachTo: { id: 'core', input: 'root' },
+            disabled: false,
+          },
+          {
+            id: 'core.nav',
+            attachTo: { id: 'core.layout', input: 'nav' },
+            disabled: true,
+          },
+        ],
+      },
+    ]);
+  });
+});