chore(beta): guard branch-sync output handling

Author: umanamente

scripts/branch-sync.js

@@ -5,10 +5,12 @@ const { getPromotePlan, getSyncBetaPlan } = require('./branch-sync-utils');
 // Wrapper around git commands used by the release workflows.
 // Keeping this logic in a script makes the YAML shorter and easier to review.
 function runGit(args, options = {}) {
-  return execFileSync('git', args, {
+  const output = execFileSync('git', args, {
     encoding: 'utf8',
     ...options,
-  }).trim();
+  });
+
+  return typeof output === 'string' ? output.trim() : '';
 }
 
 // GitHub Actions exposes a file path for step outputs through GITHUB_OUTPUT.
@@ -156,4 +158,11 @@ function main() {
   throw new Error(`Unsupported mode "${mode}". Expected "sync-beta" or "promote-master".`);
 }
 
-main();
+if (require.main === module) {
+  main();
+}
+
+module.exports = {
+  runGit,
+  main,
+};

test/UnitTests/BranchSync.test.ts

@@ -0,0 +1,27 @@
+jest.mock('child_process', () => ({
+  execFileSync: jest.fn(),
+}));
+
+const { execFileSync } = require('child_process');
+const { runGit } = require('../../scripts/branch-sync');
+
+describe('branch-sync', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should trim captured git output', () => {
+    execFileSync.mockReturnValue('  ok \n');
+
+    expect(runGit(['status'])).toBe('ok');
+    expect(execFileSync).toHaveBeenCalledWith('git', ['status'], expect.objectContaining({
+      encoding: 'utf8',
+    }));
+  });
+
+  it('should return an empty string when stdio is inherited', () => {
+    execFileSync.mockReturnValue(null);
+
+    expect(runGit(['checkout', '-B', 'beta', 'origin/beta'], { stdio: 'inherit' })).toBe('');
+  });
+});