Run test tearDowns and clean up temporary directories when a signal is caught.

test/runner/runner_test.dart

 // Copyright (c) 2015, 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.
 
 @TestOn("vm")
 
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:test/src/util/exit_codes.dart' as exit_codes;
+import 'package:test/src/util/io.dart';
 import 'package:test/test.dart';
 
 import '../io.dart';
 
 String _sandbox;
 
 final _success = """
 import 'dart:async';
 
 import 'package:test/test.dart';
@@ skipping 23 matching lines @@
 -N, --plain-name    A plain-text substring of the name of the test to run.
 -p, --platform      The platform(s) on which to run the tests.
                     [vm (default), chrome]
 
     --[no-]color    Whether to use terminal colors.
                     (auto-detected by default)
 """;
 
 void main() {
   setUp(() {
-    _sandbox = Directory.systemTemp.createTempSync('test_').path;
+    _sandbox = createTempDir();
   });
 
   tearDown(() {
     new Directory(_sandbox).deleteSync(recursive: true);
   });
 
   test("prints help information", () {
     var result = _runUnittest(["--help"]);
     expect(result.stdout, equals("""
 Runs tests in this package.
@@ skipping 305 matching lines @@
       });
     });
   });
 }
 
 ProcessResult _runUnittest(List<String> args) =>
     runUnittest(args, workingDirectory: _sandbox);
 
 ProcessResult _runDart(List<String> args) =>
     runDart(args, workingDirectory: _sandbox);