Add utility method to SubscriptionManager

pkg/analyzer_plugin/test/utilities/subscriptions/subscription_manager_test.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:analyzer_plugin/protocol/protocol_generated.dart';
 import 'package:analyzer_plugin/utilities/subscriptions/subscription_manager.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 void main() {
   defineReflectiveTests(SubscriptionManagerTest);
 }
 
 @reflectiveTest
 class SubscriptionManagerTest {
   SubscriptionManager manager = new SubscriptionManager();
 
+  String fooPath = '/project/lib/foo.dart';
+  String barPath = '/project/lib/bar.dart';
+  String bazPath = '/project/lib/baz.dart';
+
+  test_hasSubscriptionForFile_differentSubscription() {
+    manager.setSubscriptions({
+      AnalysisService.NAVIGATION: [barPath]
+    });
+    expect(manager.hasSubscriptionForFile(fooPath, AnalysisService.HIGHLIGHTS),
+        isFalse);
+  }
+
+  test_hasSubscriptionForFile_hasSubscription() {
+    manager.setSubscriptions({
+      AnalysisService.HIGHLIGHTS: [fooPath]
+    });
+    expect(manager.hasSubscriptionForFile(fooPath, AnalysisService.HIGHLIGHTS),
+        isTrue);
+  }
+
+  test_hasSubscriptionForFile_noSubscription() {
+    expect(manager.hasSubscriptionForFile(fooPath, AnalysisService.HIGHLIGHTS),
+        isFalse);
+  }
+
   test_servicesForFile() {
     expect(manager.servicesForFile('/project/lib/test.dart'), hasLength(0));
   }
 
   test_setSubscriptions() {
-    String fooPath = '/project/lib/foo.dart';
-    String barPath = '/project/lib/bar.dart';
-    String bazPath = '/project/lib/baz.dart';
     //
     // Set the initial set of subscriptions.
     //
     Map<String, List<AnalysisService>> newSubscriptions =
         manager.setSubscriptions({
       AnalysisService.HIGHLIGHTS: [fooPath, barPath],
       AnalysisService.NAVIGATION: [fooPath]
     });
 
     expect(
@@ skipping 25 matching lines @@
             [AnalysisService.HIGHLIGHTS, AnalysisService.NAVIGATION]));
     expect(manager.servicesForFile(bazPath),
         unorderedEquals([AnalysisService.HIGHLIGHTS]));
 
     expect(newSubscriptions[barPath],
         unorderedEquals([AnalysisService.NAVIGATION]));
     expect(newSubscriptions[bazPath],
         unorderedEquals([AnalysisService.HIGHLIGHTS]));
   }
 }