Add RuntimeError to default expectations and handle expectation groups correctly.

pkg/testing/lib/src/stdio_process.dart

 // Copyright (c) 2016, 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.md file.
 
 library testing.stdio_process;
 
 import 'dart:async' show EventSink, Future, Stream, StreamTransformer, Timer;
 
 import 'dart:convert' show UTF8;
 
 import 'dart:io' show Process, ProcessSignal, Stdout;
 
 import 'dart:io' as io show stderr, stdout;
 
 import 'chain.dart' show Result;
 
+import 'expectation.dart' show ExpectationSet;
+
 class StdioProcess {
   final int exitCode;
 
   final String output;
 
   StdioProcess(this.exitCode, this.output);
 
   Result<int> toResult({int expected: 0}) {
     if (exitCode == expected) {
       return new Result<int>.pass(exitCode);
     } else {
-      return new Result<int>.fail(exitCode, output);
+      return new Result<Program>(
+          exitCode, ExpectationSet.Default["RuntimeError"], output, null);
     }
   }
 
   static StreamTransformer<String, String> transformToStdio(Stdout stdio) {
     return new StreamTransformer<String, String>.fromHandlers(
         handleData: (String data, EventSink<String> sink) {
       sink.add(data);
       stdio.write(data);
     });
   }
@@ skipping 34 matching lines @@
     Future<List<String>> stdoutFuture = stdoutStream.toList();
     Future<List<String>> stderrFuture = stderrStream.toList();
     int exitCode = await process.exitCode;
     timer?.cancel();
     sb.writeAll(await stdoutFuture);
     sb.writeAll(await stderrFuture);
     await closeFuture;
     return new StdioProcess(exitCode, "$sb");
   }
 }