Make it easier to run engine tests

pkg/analyzer/test/parse_compilation_unit_test.dart

 // Copyright (c) 2013, 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.parse.compilation.unit;
+
 import 'package:analyzer/analyzer.dart';
 import 'package:unittest/unittest.dart';
 
 void main() {
   test("parses a valid compilation unit successfully", () {
     var unit = parseCompilationUnit("void main() => print('Hello, world!');");
     expect(unit.toString(), equals("void main() => print('Hello, world!');"));
   });
 
   test("throws errors for an invalid compilation unit", () {
     expect(() {
       parseCompilationUnit("void main() => print('Hello, world!')",
           name: 'test.dart');
     }, throwsA(predicate((error) {
       return error is AnalyzerErrorGroup &&
           error.toString().contains("Error in test.dart: Expected to find ';'");
     })));
   });
 
   test("defaults to '<unknown source>' if no name is provided", () {
     expect(() {
       parseCompilationUnit("void main() => print('Hello, world!')");
     }, throwsA(predicate((error) {
       return error is AnalyzerErrorGroup &&
           error.toString().contains("Error in <unknown source>: Expected to find ';'");
     })));
   });
 }