fixup! TF-4224 Reduce ReDoS vulnerability

core/test/utils/redos_vulnerability_test.dart

@@ -65,7 +65,7 @@ void main() {
       });
     });
 
-    group('NormalizeLineHeightInStyleTransformer', () {
+    group('NormalizeLineHeightInStyleTransformer tests regex patterns in isolation', () {
       test('should handle very long style strings efficiently', () {
         final longStyle = 'color: red; ' * 10000 + 'line-height: 1px;';
 
@@ -447,16 +447,16 @@ void main() {
     });
 
     group('AppUtils._emailLocalhostRegex', () {
+      final localhostRegex = RegExp(
+        r'^(?:"[^"\r\n]+"|[^<>()[\]\\.,;:\s@"]+(?:\.[^<>()[\]\\.,;:\s@"]+)*)@localhost$',
+      );
       test('should handle very long email addresses efficiently', () {
         final longEmail = '${'a' * 10000}@localhost';
 
         final stopwatch = Stopwatch()..start();
         // Note: We can't directly test AppUtils.isEmailLocalhost in core tests
         // But we can test the regex pattern
-        final regex = RegExp(
-          r'^(?:"[^"\r\n]+"|[^<>()[\]\\.,;:\s@"]+(?:\.[^<>()[\]\\.,;:\s@"]+)*)@localhost$',
-        );
-        final result = regex.hasMatch(longEmail);
+        final result = localhostRegex.hasMatch(longEmail);
         stopwatch.stop();
 
         expect(stopwatch.elapsedMilliseconds, lessThan(100));
@@ -464,10 +464,6 @@ void main() {
       });
 
       test('should correctly match valid localhost emails', () {
-        final regex = RegExp(
-          r'^(?:"[^"\r\n]+"|[^<>()[\]\\.,;:\s@"]+(?:\.[^<>()[\]\\.,;:\s@"]+)*)@localhost$',
-        );
-
         const validEmails = [
           'user@localhost',
           'user.name@localhost',
@@ -475,16 +471,12 @@ void main() {
         ];
 
         for (final email in validEmails) {
-          expect(regex.hasMatch(email.trim()), isTrue,
+          expect(localhostRegex.hasMatch(email.trim()), isTrue,
               reason: 'Should match: $email');
         }
       });
 
       test('should reject invalid localhost emails', () {
-        final regex = RegExp(
-          r'^(?:"[^"\r\n]+"|[^<>()[\]\\.,;:\s@"]+(?:\.[^<>()[\]\\.,;:\s@"]+)*)@localhost$',
-        );
-
         const invalidEmails = [
           'user@localhost.com',
           '@localhost',
@@ -493,7 +485,7 @@ void main() {
         ];
 
         for (final email in invalidEmails) {
-          expect(regex.hasMatch(email.trim()), isFalse,
+          expect(localhostRegex.hasMatch(email.trim()), isFalse,
               reason: 'Should not match: $email');
         }
       });