Strong-mode error code validation "enum" (#25117).

pkg/analyzer/test/src/task/options_test.dart

Index: pkg/analyzer/test/src/task/options_test.dart
diff --git a/pkg/analyzer/test/src/task/options_test.dart b/pkg/analyzer/test/src/task/options_test.dart
index 75c0a5a890339a34270c384d88437d4a9727fc21..eacff8966f0f45321390d8037e22fb9742742979 100644
--- a/pkg/analyzer/test/src/task/options_test.dart
+++ b/pkg/analyzer/test/src/task/options_test.dart
@@ -284,6 +284,16 @@ analyzer:
         [AnalysisOptionsWarningCode.UNSUPPORTED_VALUE]);
   }
 
+  test_analyzer_strong_mode_error_code_supported() {
+    validate(
+        '''
+analyzer:
+  errors:
+    strong_mode_assignment_cast: ignore
+''',
+        []);
+  }
+
   test_analyzer_supported_exclude() {
     validate(
         '''