Switch analysis_server to use 'package:test'.

pkg/analysis_server/test/search/element_references_test.dart

Index: pkg/analysis_server/test/search/element_references_test.dart
diff --git a/pkg/analysis_server/test/search/element_references_test.dart b/pkg/analysis_server/test/search/element_references_test.dart
index cdd7e13dfee655fe151d69154e638f531e8d88dd..bc7693fd85085a628ed6ccf95b1377b09544384b 100644
--- a/pkg/analysis_server/test/search/element_references_test.dart
+++ b/pkg/analysis_server/test/search/element_references_test.dart
@@ -8,16 +8,18 @@ import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/services/index/index.dart';
+import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
-import 'package:unittest/unittest.dart';
 
 import '../utils.dart';
 import 'abstract_search_domain.dart';
 
 main() {
   initializeTestEnvironment();
-  defineReflectiveTests(ElementReferencesTest);
-  defineReflectiveTests(_NoSearchEngine);
+  defineReflectiveSuite(() {
+    defineReflectiveTests(ElementReferencesTest);
+    defineReflectiveTests(_NoSearchEngine);
+  });
 }
 
 @reflectiveTest