More tests for creating undefined methods and functions.

pkg/analysis_testing/lib/mock_sdk.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 testing.mock_sdk;
 
 import 'package:analyzer/file_system/file_system.dart' as resource;
 import 'package:analyzer/file_system/memory_file_system.dart' as resource;
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 
 class MockSdk implements DartSdk {
   final resource.MemoryResourceProvider provider =
       new resource.MemoryResourceProvider();
 
   MockSdk() {
     // TODO(paulberry): Add to this as needed.
     const Map<String, String> pathToContent = const {
       "/lib/core/core.dart": '''
           library dart.core;
           class Object {}
           class Function {}
           class StackTrace {}
           class Symbol {}
           class Type {}
 
-          class String extends Object {}
+          abstract class Comparable<T> {
+            int compareTo(T other);
+          }
+
+          class String implements Comparable<String> {
+          }
+
           class bool extends Object {}
-          abstract class num extends Object {
+          abstract class num implements Comparable<num> {
             num operator +(num other);
             num operator -(num other);
             num operator *(num other);
             num operator /(num other);
             int toInt();
           }
           abstract class int extends num {
             int operator -();
           }
           class double extends num {}
@@ skipping 88 matching lines @@
     if (path != null) {
       resource.File file = provider.getResource(path);
       return file.createSource(UriKind.DART_URI);
     }
 
     // If we reach here then we tried to use a dartUri that's not in the
     // table above.
     throw unimplemented;
   }
 }