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

lib/src/runner/vm/isolate_listener.dart

Index: lib/src/runner/vm/isolate_listener.dart
diff --git a/lib/src/runner/vm/isolate_listener.dart b/lib/src/runner/vm/isolate_listener.dart
index c0e7c09c7fcf2f6fbb797479816a0134cf7b86d1..46c05f2592c70c8e09abdd8a61609a80ec76da1e 100644
--- a/lib/src/runner/vm/isolate_listener.dart
+++ b/lib/src/runner/vm/isolate_listener.dart
@@ -97,6 +97,15 @@ class IsolateListener {
   void _runTest(Test test, SendPort sendPort) {
     var liveTest = test.load(_suite);
 
+    var receivePort = new ReceivePort();
+    sendPort.send({"type": "started", "reply": receivePort.sendPort});
+
+    receivePort.listen((message) {
+      assert(message['command'] == 'close');
+      receivePort.close();
+      liveTest.close();
+    });
+
     liveTest.onStateChange.listen((state) {
       sendPort.send({
         "type": "state-change",