the real fix

packages/fluentui/projects-test/assets/cra/App.tsx

@@ -1,4 +1,3 @@
-/** @jsxRuntime classic */
 import {
   Accordion,
   Animation,

packages/fluentui/projects-test/src/createReactApp.ts

@@ -33,6 +33,16 @@ async function prepareApp(tmpDirectory: string, appName: string): Promise<string
   return appProjectPath;
 }
 
+async function fixTypescript(testAppPath: string) {
+  // TS 4.1 emits an import of `react/jsx-runtime` which doesn't exist in the types as of writing.
+  // Temporary workaround is to downgrade to 4.0.
+  await sh('yarn add typescript@~4.0.0', testAppPath);
+  // Also revert the change to the "jsx" tsconfig setting
+  const tsconfigPath = path.join(testAppPath, 'tsconfig.json');
+  const tsconfigContent = fs.readFileSync(tsconfigPath, 'utf8');
+  fs.writeFileSync(tsconfigPath, tsconfigContent.replace('react-jsx', 'react'));
+}
+
 /**
  * Tests the following scenario:
  *  - Create a new react test app
@@ -49,7 +59,9 @@ export async function createReactApp() {
   logger('STEP 1. Create test React project with TSX scripts..');
 
   const testAppPath = config.paths.withRootAt(await prepareApp(tmpDirectory, 'test-app'));
+  await fixTypescript(testAppPath());
   logger(`Test React project is successfully created: ${testAppPath()}`);
+
   logger('STEP 2. Add Fluent UI dependency to test project..');
 
   const packedPackages = await packProjectPackages(logger);