Improve error reporting in ID tests

Change-Id: I3a1da7cef955cdef62d4fea3a98f5949309695be
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/124240
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>

Author: stereotype441

pkg/analyzer/test/util/id_testing_helper.dart

@@ -13,6 +13,7 @@ import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/analysis/utilities.dart';
 import 'package:analyzer/dart/ast/ast.dart' hide Annotation;
 import 'package:analyzer/diagnostic/diagnostic.dart';
+import 'package:analyzer/error/error.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/dart/analysis/byte_store.dart';
@@ -141,7 +142,12 @@ Future<bool> runTestForConfig<T>(
   var errors =
       result.errors.where((e) => e.severity == Severity.error).toList();
   if (errors.isNotEmpty) {
-    onFailure('Errors found:\n  ${errors.join('\n  ')}');
+    String _formatError(AnalysisError e) {
+      var locationInfo = result.unit.lineInfo.getLocation(e.offset);
+      return '$locationInfo: ${e.message}';
+    }
+
+    onFailure('Errors found:\n  ${errors.map(_formatError).join('\n  ')}');
     return true;
   }
   Map<Uri, Map<Id, ActualData<T>>> actualMaps = <Uri, Map<Id, ActualData<T>>>{};