Add a --pause-after-load flag for debugging.

lib/src/backend/live_test_controller.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.
 
 library test.backend.live_test_controller;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:stack_trace/stack_trace.dart';
@@ skipping 133 matching lines @@
   /// it's not different, this does nothing.
   void setState(State newState) {
     if (_isClosed) return;
     if (_state == newState) return;
 
     _state = newState;
     _onStateChangeController.add(newState);
   }
 
   /// Emits a line printed by the test over [LiveTest.onPrint].
-  void print(String line) => _onPrintController.add(line);
+  void print(String line) {
+    if (_onPrintController.hasListener) {

[kevmoo, 2015/07/23 20:47:03]

what's a case where the controller has no listener?

[nweiz, 2015/07/23 21:23:00]

After the test package has received a signal, it will unsubscribe everything,
but we may still want to see prints for debugging purposes.

+      _onPrintController.add(line);
+    } else {
+      // Make sure all prints get surfaced one way or another to aid in
+      // debugging.
+      Zone.ROOT.print(line);
+    }
+  }
 
   /// A wrapper for [_onRun] that ensures that it follows the guarantees for
   /// [LiveTest.run].
   Future _run() {
     if (_runCalled) {
       throw new StateError("LiveTest.run() may not be called more than once.");
     } else if (_isClosed) {
       throw new StateError("LiveTest.run() may not be called for a closed "
           "test.");
     }
@@ skipping 12 matching lines @@
 
     if (_runCalled) {
       _onClose();
     } else {
       completer.complete();
     }
 
     return completer.future;
   }
 }