Emits additional output when test_runner_test fails.

tests/standalone/io/test_runner_test.dart

 // Copyright (c) 2013, 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.
 
 import "dart:io";
 import "dart:isolate";
 import "dart:async";
 import "../../../tools/testing/dart/test_runner.dart";
 import "../../../tools/testing/dart/test_suite.dart";
 import "../../../tools/testing/dart/test_progress.dart" as progress;
 import "../../../tools/testing/dart/status_file_parser.dart";
 import "../../../tools/testing/dart/test_options.dart";
 import "process_test_util.dart";
 
 final DEFAULT_TIMEOUT = 2;
 final LONG_TIMEOUT = 30;
 
 class TestController {
   static int numTests = 0;
   static int numCompletedTests = 0;
 
   // Used as TestCase.completedCallback.
   static processCompletedTest(TestCase testCase) {
     numCompletedTests++;
     if (testCase.displayName == "fail-unexpected") {
       if (!testCase.unexpectedOutput) {
-        throw "Expected fail-unexpected";
+        var stdout =
+            new String.fromCharCodes(testCase.lastCommandOutput.stdout);
+        var stderr =
+            new String.fromCharCodes(testCase.lastCommandOutput.stderr);
+        print("stdout = [$stdout]");
+        print("stderr = [$stderr]");
+        throw "Expected fail-unexpected: ${testCase.result}";
       }
     } else {
       if (testCase.unexpectedOutput) {
+        var stdout =
+            new String.fromCharCodes(testCase.lastCommandOutput.stdout);
+        var stderr =
+            new String.fromCharCodes(testCase.lastCommandOutput.stderr);
+        print("stdout = [$stdout]");
+        print("stderr = [$stderr]");
         throw "Unexpected fail";
       }
     }
   }
 
   static void finished() {
     if (numTests != numCompletedTests) {
       throw "bad completion count. "
             "expected: $numTests, actual: $numCompletedTests";
     }
@@ skipping 88 matching lines @@
         break;
       case 'timeout':
         // Run for 10 seconds, then exit.  This tests a 2 second timeout.
         new Timer(new Duration(seconds: 10), (){ });
         break;
       default:
         throw "Unknown option ${arguments[0]} passed to test_runner_test";
     }
   }
 }