Use the new test runner.

test/error_group_test.dart

Index: test/error_group_test.dart
diff --git a/test/error_group_test.dart b/test/error_group_test.dart
index cd85f155af8d220bff1ed6bafcdf737d7bc47f05..cc2616d6c02f6a2e62552b53ac45fce6ea3daf90 100644
--- a/test/error_group_test.dart
+++ b/test/error_group_test.dart
@@ -8,7 +8,7 @@ import 'dart:async';
 
 import 'package:pub/src/error_group.dart';
 import 'package:pub/src/utils.dart';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 
 ErrorGroup errorGroup;