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

test/runner/parse_metadata_test.dart

Index: test/runner/parse_metadata_test.dart
diff --git a/test/runner/parse_metadata_test.dart b/test/runner/parse_metadata_test.dart
index e65b62a2ead0ca479c2b0703aabae233158a46eb..72c2b4cfe76d530b18d3f1da4482876fb91949f7 100644
--- a/test/runner/parse_metadata_test.dart
+++ b/test/runner/parse_metadata_test.dart
@@ -11,13 +11,14 @@ import 'package:test/test.dart';
 import 'package:test/src/backend/platform_selector.dart';
 import 'package:test/src/backend/test_platform.dart';
 import 'package:test/src/runner/parse_metadata.dart';
+import 'package:test/src/util/io.dart';
 
 String _sandbox;
 String _path;
 
 void main() {
   setUp(() {
-    _sandbox = Directory.systemTemp.createTempSync('test_').path;
+    _sandbox = createTempDir();
     _path = p.join(_sandbox, "test.dart");
   });