Use the fact that some index lists are sorted.

pkg/analysis_server/test/services/index2/index2_test.dart

 // Copyright (c) 2016, 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:analysis_server/src/services/index2/index2.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/summary/idl.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
@@ skipping 150 matching lines @@
 }
 main(A a, p) {
   a.test(); // a-inv-r-q
   a.test = 1; // a-ref-r-q
   a.test += 2; // a-ref-r-q
   print(a.test); // a-ref-r-q
   p.test(); // p-inv-ur-q
   p.test = 1; // p-ref-ur-q
   p.test += 2; // p-ref-ur-q
   print(p.test); // p-ref-ur-q
+  print(p.test2); // not requested
 }
 ''');
     List<Location> locations =
         await index.getUnresolvedMemberReferences('test');
     expect(locations, hasLength(4));
     findLocationTest(locations, 'test(); // p-inv-ur-q');
     findLocationTest(locations, 'test = 1; // p-ref-ur-q');
     findLocationTest(locations, 'test += 2; // p-ref-ur-q');
     findLocationTest(locations, 'test); // p-ref-ur-q');
   }
@@ skipping 22 matching lines @@
     index.indexUnit(testUnit);
   }
 
   Source _indexUnit(String path, String code) {
     Source source = addSource(path, code);
     CompilationUnit unit = resolveLibraryUnit(source);
     index.indexUnit(unit);
     return source;
   }
 }