From c937439e875ab5072aa2605686d2f103b8f8ea0c Mon Sep 17 00:00:00 2001
From: Alex Hunt <huntie@meta.com>
Date: Thu, 22 May 2025 09:44:15 -0700
Subject: [PATCH] Add a basic Jest test to helloworld (#51534)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51534

Aims to give us CI coverage of React Native's Jest preset, preventing future bugs like https://github.com/facebook/react-native/pull/51525.

Changes:
- Add a basic "it renders" Jest test to helloworld
- Add "Run Helloworld tests" step to `test-ios-helloworld` job in CI
- Also convert helloworld's `App.tsx` to TypeScript, as easiest way to unblock Jest JSX behaviour.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D75218901

fbshipit-source-id: 601155c59c4483696971df4c29d51549d97f49f2
---
 .github/actions/test-ios-helloworld/action.yml |  8 +++++++-
 packages/helloworld/{App.jsx => App.tsx}       |  3 +--
 packages/helloworld/__tests__/App.test.tsx     | 18 ++++++++++++++++++
 packages/helloworld/package.json               |  2 ++
 packages/helloworld/tsconfig.json              |  3 +++
 yarn.lock                                      |  8 ++++++++
 6 files changed, 39 insertions(+), 3 deletions(-)
 rename packages/helloworld/{App.jsx => App.tsx} (94%)
 create mode 100644 packages/helloworld/__tests__/App.test.tsx
 create mode 100644 packages/helloworld/tsconfig.json

diff --git a/.github/actions/test-ios-helloworld/action.yml b/.github/actions/test-ios-helloworld/action.yml
index 6a7c7367e29..e85cad17a77 100644
--- a/.github/actions/test-ios-helloworld/action.yml
+++ b/.github/actions/test-ios-helloworld/action.yml
@@ -83,7 +83,13 @@ runs:
 
         yarn bootstrap ios "${args[@]}" | cat
 
-    - name: Build HelloWorld  project
+    - name: Run Helloworld tests
+      shell: bash
+      run: |
+        cd packages/helloworld
+        yarn test
+
+    - name: Build HelloWorld project
       shell: bash
       run: |
         cd packages/helloworld
diff --git a/packages/helloworld/App.jsx b/packages/helloworld/App.tsx
similarity index 94%
rename from packages/helloworld/App.jsx
rename to packages/helloworld/App.tsx
index 9bbe08bbaed..09f7928a852 100644
--- a/packages/helloworld/App.jsx
+++ b/packages/helloworld/App.tsx
@@ -4,7 +4,6 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @flow strict-local
  * @format
  */
 
@@ -19,7 +18,7 @@ import {
   useColorScheme,
 } from 'react-native';
 
-function App(): React.Node {
+function App(): React.ReactNode {
   const isDarkMode = useColorScheme() === 'dark';
 
   return (
diff --git a/packages/helloworld/__tests__/App.test.tsx b/packages/helloworld/__tests__/App.test.tsx
new file mode 100644
index 00000000000..399fc98c4b4
--- /dev/null
+++ b/packages/helloworld/__tests__/App.test.tsx
@@ -0,0 +1,18 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import App from '../App';
+import React from 'react';
+import ReactTestRenderer from 'react-test-renderer';
+
+test('renders correctly', async () => {
+  await ReactTestRenderer.act(() => {
+    ReactTestRenderer.create(<App />);
+  });
+});
diff --git a/packages/helloworld/package.json b/packages/helloworld/package.json
index bc92f858d55..82448d2dd67 100644
--- a/packages/helloworld/package.json
+++ b/packages/helloworld/package.json
@@ -23,6 +23,8 @@
     "@react-native/core-cli-utils": "0.80.0-main",
     "@react-native/eslint-config": "0.80.0-main",
     "@react-native/metro-config": "0.80.0-main",
+    "@react-native/typescript-config": "0.80.0-main",
+    "@types/jest": "^29.5.14",
     "chalk": "^4.1.2",
     "commander": "^12.0.0",
     "eslint": "^8.19.0",
diff --git a/packages/helloworld/tsconfig.json b/packages/helloworld/tsconfig.json
new file mode 100644
index 00000000000..88fa317f10c
--- /dev/null
+++ b/packages/helloworld/tsconfig.json
@@ -0,0 +1,3 @@
+{
+  "extends": "@react-native/typescript-config"
+}
diff --git a/yarn.lock b/yarn.lock
index e1770521d2a..878a4cc3eb5 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1918,6 +1918,14 @@
   dependencies:
     "@types/istanbul-lib-report" "*"
 
+"@types/jest@^29.5.14":
+  version "29.5.14"
+  resolved "https://registry.yarnpkg.com/@types/jest/-/jest-29.5.14.tgz#2b910912fa1d6856cadcd0c1f95af7df1d6049e5"
+  integrity sha512-ZN+4sdnLUbo8EVvVc2ao0GFW6oVrQRPn4K2lglySj7APvSrgzxHiNNK99us4WDMi57xxA2yggblIAMNhXOotLQ==
+  dependencies:
+    expect "^29.0.0"
+    pretty-format "^29.0.0"
+
 "@types/jest@^29.5.3":
   version "29.5.12"
   resolved "https://registry.yarnpkg.com/@types/jest/-/jest-29.5.12.tgz#7f7dc6eb4cf246d2474ed78744b05d06ce025544"