NullError in unit test

Question

I am having problems writing a test. In general, all method calls inside of expect() fail with NullError. The same methods can be successfully called outside of expect(). Here is my main() method:

    ...

        import 'package:unittest/unittest.dart';
        import 'package:unittest/html_config.dart';


        void main() {  
          useHtmlConfiguration();

          test('URL connection is Ok for${repositoryURL} ', (){
              var httpRequest = new HttpRequest();
              expect(httpRequest.open('POST', repositoryURL), returnsNormally, reason:"httpRequestOpen for ${repositoryURL} threw exception");
          }); 
          //    httpRequest.open('POST', repositoryURL); // Works if not within the expect

          test('Repositories request is sent',(){
              expect (sendRepositoryListRequest(), returnsNormally, reason:"sendRepositoryListRequest threw exception");
          });   
           //sendRepositoryListRequest(); // works if not within the expect

Browser output:

FAIL 1  FAIL    Expectation: URL connection is Ok for../ServiceDirect/getRepositories . 
Expected: return normally Actual: <null> Which: threw W0: <NullError:  Cannot call "call$0" on null> 
httpRequestOpen for     ../ServiceDirect/getRepositories threw exception 
documentviewertest.dart.js 1224:3   dart.b     
documentviewertest.dart.js 7665:20  Gc.Is.JX 
documentviewertest.dart.js 7637:25  kw.xu 
documentviewertest.dart.js 7985:3   dart.vd 
documentviewertest.dart.js 6792:22  QA.call$0 
documentviewertest.dart.js 7776:30  c9.Sp 
documentviewertest.dart.js 7840:10  Rm.call$1 
documentviewertest.dart.js 2510:34  vs.GP 
documentviewertest.dart.js 2643:25  jb.call$0 
documentviewertest.dart.js 2456:26  T8 
2   FAIL    Expectation: Repositories request is sent. 
Expected: return normally Actual: <null> Which: threw W0: <NullError: Cannot call "call$0" on null> 
sendRepositoryListRequest threw exception  
documentviewertest.dart.js 1224:3   dart.b  
documentviewertest.dart.js 7665:20  Gc.Is.JX 
documentviewertest.dart.js 7637:25  kw.xu 
documentviewertest.dart.js 7985:3   dart.vd 
documentviewertest.dart.js 6796:22  Cv.call$0 
documentviewertest.dart.js 7776:30  c9.Sp 
documentviewertest.dart.js 7840:10  Rm.call$1 
documentviewertest.dart.js 2510:34  vs.GP 
documentviewertest.dart.js 2643:25  jb.call$0  
documentviewertest.dart.js 2456:26  T8 

Total 0 passed, 2 failed 0 errors

Output when running in DART (not browser)

    unittest-suite-wait-for-done
    FAIL: Testing URL connection for../ServiceDirect/getRepositories 
    Expected: return normally
    Actual: <null>
     Which: threw NoSuchMethodError:<The null object does not have a method 'call'.

  NoSuchMethodError : method not found: 'call'
  Receiver: null
  Arguments: []>
  httpRequestOpen for ../ServiceDirect/getRepositories threw exception

  package:unittest/src/simple_configuration.dart 137:7                                                             SimpleConfiguration.onExpectFailure
  package:unittest/src/simple_configuration.dart 15:28                                                             _ExpectFailureHandler.fail
  package:unittest/src/expect.dart 117:9                                                                           DefaultFailureHandler.failMatch
  package:unittest/src/expect.dart 75:29                                                                           expect
  documentviewertest.dart 606:13                                                                                   main.<fn>
  package:unittest/src/test_case.dart 111:31                                                                       _run.<fn>
  dart:async/future_impl.dart 453                                                                                  _Future._propagateToListeners.<fn>
  dart:async/zone.dart 683                                                                                         _rootRun
  dart:async/zone.dart 417                                                                                         _ZoneDelegate.run
  dart:async/zone.dart 627                                                                                         _CustomizedZone.run
  dart:async/future_impl.dart 445                                                                                  _Future._propagateToListeners
  dart:async/future_impl.dart 303                                                                                  _Future._complete
  dart:async/future_impl.dart 354                                                                                  _Future._asyncComplete.<fn>
  dart:async/zone.dart 688                                                                                         _rootRun
  dart:async/zone.dart 417                                                                                         _ZoneDelegate.run
  dart:async/zone.dart 627                                                                                         _CustomizedZone.run
  dart:async/zone.dart 538                                                                                         _BaseZone.runGuarded
  dart:async/zone.dart 563                                                                                         _BaseZone.bindCallback.<fn>
  dart:async/schedule_microtask.dart 18                                                                            _asyncRunCallback
  file:///E:/b/build/slave/dartium-win-full-stable/build/src/dart/tools/dom/src/native_DOMImplementation.dart 604  _handleMutation
FAIL: Repositories request is sent
  Expected: return normally
    Actual: <null>
     Which: threw NoSuchMethodError:<The null object does not have a method 'call'.

  NoSuchMethodError : method not found: 'call'
  Receiver: null
  Arguments: []>
  *** sendRepositoryListRequest threw exception ***

  package:unittest/src/simple_configuration.dart 137:7                                                             SimpleConfiguration.onExpectFailure
  package:unittest/src/simple_configuration.dart 15:28                                                             _ExpectFailureHandler.fail
  package:unittest/src/expect.dart 117:9                                                                           DefaultFailureHandler.failMatch
  package:unittest/src/expect.dart 75:29                                                                           expect
  documentviewertest.dart 613:14                                                                                   main.<fn>
  package:unittest/src/test_case.dart 111:31                                                                       _run.<fn>
  dart:async/future_impl.dart 453                                                                                  _Future._propagateToListeners.<fn>
  dart:async/zone.dart 683                                                                                         _rootRun
  dart:async/zone.dart 417                                                                                         _ZoneDelegate.run
  dart:async/zone.dart 627                                                                                         _CustomizedZone.run
  dart:async/future_impl.dart 445                                                                                  _Future._propagateToListeners
  dart:async/future_impl.dart 303                                                                                  _Future._complete
  dart:async/future_impl.dart 354                                                                                  _Future._asyncComplete.<fn>
  dart:async/zone.dart 688                                                                                         _rootRun
  dart:async/zone.dart 417                                                                                         _ZoneDelegate.run
  dart:async/zone.dart 627                                                                                         _CustomizedZone.run
  dart:async/zone.dart 538                                                                                         _BaseZone.runGuarded
  dart:async/zone.dart 563                                                                                         _BaseZone.bindCallback.<fn>
  dart:async/schedule_microtask.dart 18                                                                            _asyncRunCallback
  file:///E:/b/build/slave/dartium-win-full-stable/build/src/dart/tools/dom/src/native_DOMImplementation.dart 604  _handleMutation

0 PASSED, 2 FAILED, 0 ERRORS
Exception: Exception: Some tests failed.
  SimpleConfiguration.onDone (package:unittest/src/simple_configuration.dart:209:9)
  _completeTests@0x398acc1e (package:unittest/unittest.dart:663:17)
  _runTest@0x398acc1e (package:unittest/unittest.dart:612:19)
  _nextTestCase@0x398acc1e (package:unittest/unittest.dart:532:11)

Thank you, Yuri.

Are you running this as JavaScript? I would expect for example `documentviewerDiv` to be null. Nothing in your code indicates that it should have a value. — Günter Zöchbauer, Mar 17 '14 at 16:10
I think you should reduce your code to one expect call that allows to reproduce your problem and drop the other code and other output. — Günter Zöchbauer, Mar 17 '14 at 16:16
I cut down the code only to problematic tests. I do not think that sendRepositoryListRequest() implementation is important (it is implemented as void sendRepositoryListRequest()), since the error happends also on httpRequest.open(). — Yuri P., Mar 17 '14 at 16:24
Your output looks like you are running tests as JavaScript, have you tried to ran just the Dart code? — Günter Zöchbauer, Mar 17 '14 at 16:27
And, yes, I am running the test as JS, on both Dartium and Chrome. — Yuri P., Mar 17 '14 at 16:28
Have you tried running the tests as Dart code? You should at first ensure that is runs as Dart code and only then it makes sense to try how it works as JS. — Günter Zöchbauer, Mar 17 '14 at 16:30
I tried it in DART code. The output is added to the original post. — Yuri P., Mar 17 '14 at 16:39
You should take a look at http://stackoverflow.com/questions/15925431 — Günter Zöchbauer, Mar 17 '14 at 16:53
Forget my previous comment. `httpRequest.open()` is not async — Günter Zöchbauer, Mar 17 '14 at 16:58

score 0 · Accepted Answer · answered Mar 17 '14 at 16:58

0

this worked for me

expect(() => httpRequest.open('POST', repositoryURL), returnsNormally, reason:"httpRequestOpen for ${repositoryURL} threw exception");

answered Mar 17 '14 at 16:58

Günter Zöchbauer

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Thank you, this worked for me as well. Do you think this a bug in unit test? – Yuri P. Mar 17 '14 at 17:06
Arguments like `repositoryURL` have no meaning inside expect. You have to pass the entire expression as a closure so that for example `httpReqeust.open()` can access the actual value of `repositoryURL` when `expect` executes it. It couldn't work any other way. – Günter Zöchbauer Mar 17 '14 at 17:10

NullError in unit test

1 Answers1