new onPriorityChanged event stream

pkg/analysis_server/test/analysis_server_test.dart

 // Copyright (c) 2014, 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.
 
 library test.analysis_server;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/domain_server.dart';
 import 'package:analysis_server/src/operation/operation.dart';
@@ skipping 136 matching lines @@
         wasChanged = false;
         wasRemoved = false;
         helper.server.setAnalysisRoots('0', [], [], {});
         return pumpEventQueue();
       }).then((_) {
         expect(wasAdded, isFalse);
         expect(wasChanged, isFalse);
         expect(wasRemoved, isTrue);
       });
     });
+
+    test('priority sources changed event', () {
+      AnalysisServerTestHelper helper = new AnalysisServerTestHelper();
+      helper.resourceProvider.newFolder('/foo');
+
+      int eventCount = 0;
+      Source firstSource = null;
+      helper.server.onPriorityChange.listen((PriorityChangeEvent event) {
+        ++eventCount;
+        firstSource = event.firstSource;
+      });
+
+      helper.server.setAnalysisRoots('0', ['/foo'], [], {});
+      return pumpEventQueue().then((_) {
+        expect(eventCount, 0);
+
+        helper.server.setPriorityFiles('1', ['/foo/bar.dart']);
+        return pumpEventQueue();
+      }).then((_) {
+        expect(eventCount, 1);
+        expect(firstSource.fullName, '/foo/bar.dart');
+
+        helper.server.setPriorityFiles('2', ['/foo/b1.dart', '/foo/b2.dart']);
+        return pumpEventQueue();
+      }).then((_) {
+        expect(eventCount, 2);
+        expect(firstSource.fullName, '/foo/b1.dart');
+
+        helper.server.setPriorityFiles('17', []);
+        return pumpEventQueue();
+      }).then((_) {
+        expect(eventCount, 3);
+        expect(firstSource, isNull);
+      });
+    });
   });
 }
 
 class AnalysisServerTestHelper {
   MockServerChannel channel;
   AnalysisServer server;
   MemoryResourceProvider resourceProvider;
 
   AnalysisServerTestHelper({bool rethrowExceptions: true}) {
     channel = new MockServerChannel();
@@ skipping 12 matching lines @@
   @override
   Response handleRequest(Request request) {
     if (request.method == 'echo') {
       return new Response(request.id, result: {
         'echo': true
       });
     }
     return null;
   }
 }