Use MockSdk to speed-up tests.

pkg/analyzer2dart/test/tree_shaker_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.
 
+import 'package:analysis_testing/mock_sdk.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
+import 'package:analyzer/src/generated/sdk.dart';
+import 'package:analyzer/src/generated/source.dart';
 import 'package:unittest/unittest.dart';
 
 import '../lib/src/closed_world.dart';
 import '../lib/src/driver.dart';
 
 main() {
   test('Toplevel function', () {
     var helper = new TreeShakerTestHelper('''
 main() {
   foo();
@@ skipping 91 matching lines @@
   /**
    * Classes instantiated in [world], indexed by name.
    */
   Map<String, ClassDeclaration> instantiatedClasses = <String,
       ClassDeclaration>{};
 
   /**
    * Create a TreeShakerTestHelper based on the given file contents.
    */
   TreeShakerTestHelper(String contents) {
-    Driver driver = new Driver();
-    world =
-        driver.computeWorld(driver.resolveEntryPoint(driver.setFakeRoot(contents)));
+    DartSdk sdk = new MockSdk();
+    Driver driver = new Driver(sdk);
+    Source rootSource = driver.setFakeRoot(contents);
+    FunctionElement entryPoint = driver.resolveEntryPoint(rootSource);
+    world = driver.computeWorld(entryPoint);
     world.executableElements.forEach(
         (ExecutableElement element, Declaration node) {
       if (element is FunctionElement) {
         FunctionDeclaration declaration = node as FunctionDeclaration;
         expect(declaration, isNotNull);
         expect(declaration.element, equals(element));
         functions[element.name] = declaration;
       } else if (element is MethodElement) {
         MethodDeclaration declaration = node as MethodDeclaration;
         expect(declaration, isNotNull);
         expect(declaration.element, equals(element));
         methods['${element.enclosingElement.name}.${element.name}'] =
             declaration;
       }
     });
     world.instantiatedClasses.forEach(
         (ClassElement element, ClassDeclaration declaration) {
       expect(declaration, isNotNull);
       expect(declaration.element, equals(element));
       instantiatedClasses[element.name] = declaration;
     });
   }
 }