Switch analysis_server to use 'package:test'.

pkg/analysis_server/test/edit/assists_test.dart

Index: pkg/analysis_server/test/edit/assists_test.dart
diff --git a/pkg/analysis_server/test/edit/assists_test.dart b/pkg/analysis_server/test/edit/assists_test.dart
index 538a04ed940b7ce71ce5a3c409dbf34d3cb2b1dc..5b1acee3ccefdb19f81937b2de4246f8ba7a3998 100644
--- a/pkg/analysis_server/test/edit/assists_test.dart
+++ b/pkg/analysis_server/test/edit/assists_test.dart
@@ -7,15 +7,17 @@ library test.edit.assists;
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/edit/edit_domain.dart';
 import 'package:plugin/manager.dart';
+import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
-import 'package:unittest/unittest.dart' hide ERROR;
 
 import '../analysis_abstract.dart';
 import '../utils.dart';
 
 main() {
   initializeTestEnvironment();
-  defineReflectiveTests(AssistsTest);
+  defineReflectiveSuite(() {
+    defineReflectiveTests(AssistsTest);
+  });
 }
 
 @reflectiveTest