Unittest_vm breaks on failed asyncTests

[DartBot]

This issue was originally filed by VadimTsu...@gmail.com

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What steps will reproduce the problem?

1. Create and run dart script with async test:

import("dart:io");

import('../third_party/testing/unittest/unittest_vm.dart');

main(){
  asyncTest("Failed async test",1,(){
    Completer completer = new Completer();
    new Timer(10,(timer)=>completer.complete(1));
    completer.future.then((v){
      Expect.equals(2, v);
      callbackDone();
   });
 });
}

What is the expected output?
FAIL: Failed async test
  Expect.equals(expected: <2>, actual: <1>) fails.

0 PASSED, 1 FAILED, 0 ERRORS

What do you see instead?
Stack trace -
Unhandled exception:
Expect.equals(expected: <2>, actual: <1>) fails.
 0. Function: 'Expect._fail@127eafe4' url: 'bootstrap' line:1460 col:5
 1. Function: 'Expect.equals' url: 'bootstrap' line:1195 col:10
 2. Function: '::function' url: 'file:///C:/Dropbox/dart/Projects/mongo-dart/tests/testUnitTest.dart' line:8 col:20
 3. Function: 'FutureImpl._complete@924b4b8' url: 'bootstrap_impl' line:3126 col:17
 4. Function: 'FutureImpl._setValue@924b4b8' url: 'bootstrap_impl' line:3140 col:14
 5. Function: 'CompleterImpl.complete' url: 'bootstrap_impl' line:3209 col:26
 6. Function: '::function' url: 'file:///C:/Dropbox/dart/Projects/mongo-dart/tests/testUnitTest.dart' line:6 col:45
 7. Function: '_Timer@14117cc4._handleTimeout@14117cc4' url: 'dart:io' line:6979 col:28
 8. Function: '_Timer@14117cc4._handleTimeout@14117cc4' url: 'dart:io' line:6986 col:9
 9. Function: '_Timer@14117cc4.function' url: 'dart:io' line:6995 col:23
 10. Function: '_ReceivePortImpl@6be832b._handleMessage@6be832b' url: 'dart:isolate' line:281 col:22

What version of the product are you using? On what operating system?
Dart-sdk revision 5294
Unittest from bleeding_edge repo revision 5535
OS: Windows7, 32bit
Please provide any additional information below.

[iposva-google]

The Expect class does throw exceptions if an expectation fails. I am not entirely clear whether the unittest library should be expected to be intercepting these exceptions or not.

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cc @munificent.
cc @jmesserly.
Added Area-Test, Triaged labels.

[DartBot]

This comment was originally written by carsten....@gmail.com

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whether the unittest library should be expected to be intercepting these exceptions or not.

It seems so, because in sync tests, Expect calls(as well as the except(foo).equals(bar) shortcuts) do work as expected and without breaking the current testsuite.

As expected - not stopping the suite from running, but reporting a failed test:
test("testFoo", () => expect(2).equals(3));

Similar test - using asyncTest - is throwing instead reporting:
asyncTest("testFoo", 200, () =>
  new Timer(150, (t) { expect(2).equals(3); callbackDone(); })
);

[gramster]

Added AssumedStale label.