Don't wrap exceptions in complete or completes().

test/frontend/matcher/completion_test.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.
 
 import 'dart:async';
 
 import 'package:test/test.dart';
+import 'package:test/src/backend/state.dart';
 
 import '../../utils.dart';
 
 void main() {
   group("[completes]", () {
     test("blocks the test until the Future completes", () {
       return expectTestBlocks(() {
         var completer = new Completer();
         expect(completer.future, completes);
         return completer;
       }, (completer) => completer.complete());
     });
 
     test("with an error", () async {
       var liveTest = await runTestBody(() {
         expect(new Future.error('X'), completes);
       });
 
-      expectTestFailed(liveTest, startsWith(
-          "Expected future to complete successfully, but it failed with X"));
+      expect(liveTest.state.status, equals(Status.complete));
+      expect(liveTest.state.result, equals(Result.error));
+      expect(liveTest.errors, hasLength(1));
+      expect(liveTest.errors.first.error, equals('X'));
     });
 
     test("with a failure", () async {
       var liveTest = await runTestBody(() {
         expect(new Future.error(new TestFailure('oh no')), completes);
       });
 
       expectTestFailed(liveTest, "oh no");
     });
 
@@ skipping 19 matching lines @@
         expect(completer.future, completion(isNull));
         return completer;
       }, (completer) => completer.complete());
     });
 
     test("with an error", () async {
       var liveTest = await runTestBody(() {
         expect(new Future.error('X'), completion(isNull));
       });
 
-      expectTestFailed(liveTest, startsWith(
-          "Expected future to complete successfully, but it failed with X"));
+      expect(liveTest.state.status, equals(Status.complete));
+      expect(liveTest.state.result, equals(Result.error));
+      expect(liveTest.errors, hasLength(1));
+      expect(liveTest.errors.first.error, equals('X'));
     });
 
     test("with a failure", () async {
       var liveTest = await runTestBody(() {
         expect(new Future.error(new TestFailure('oh no')), completion(isNull));
       });
 
       expectTestFailed(liveTest, "oh no");
     });
 
@@ skipping 12 matching lines @@
         expect(new Future.value('a'), completion(equals('b')));
       });
 
       expectTestFailed(liveTest, startsWith(
           "Expected: 'b'\n"
           "  Actual: 'a'\n"
           "   Which: is different."));;
     });
   });
 }