Dart Unit Test - Always passing

Question

All,

Here is a unit test for checking the size of a collection

main() {
  test("Resource Manager Image Load", () {
    ResourceManager rm = new ResourceManager();
    int WRONG_SIZE = 1000000;

    rm.loadImageManifest("data/rm/test_images.yaml").then((_){
      print("Length="+ rm.images.length.toString()); // PRINTS '6' - WHICH IS CORRECT
      expect(rm.images, hasLength(WRONG_SIZE));
    });
  });
}

I am running this from a browser (client-side Dart libraries are in use) and it ALWAYS passes, no matter what the value of WRONG_SIZE.

Help appreciated.

score 2 · Accepted Answer · answered Sep 29 '14 at 06:15

2

In such simple cases you can just return the future. The unit test framework recognizes it and waits for the future to complete. This also works for setUp/tearDown.

main() {
  test("Resource Manager Image Load", () {
    ResourceManager rm = new ResourceManager();
    int WRONG_SIZE = 1000000;

    return rm.loadImageManifest("data/rm/test_images.yaml").then((_) {
    //^^^^
      print("Length="+ rm.images.length.toString()); // PRINTS '6' - WHICH IS CORRECT
      expect(rm.images, hasLength(WRONG_SIZE));
    });
  });
}

answered Sep 29 '14 at 06:15

Günter Zöchbauer

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Didn't realise that; much better! – Danny Tuppeny Sep 29 '14 at 06:26
I did exactly this - except I did not use the 'return rm....'. Now its working. Thx. I do find this 'async everywhere' approach with Dart takes some getting used to... – NullPumpkinException Sep 29 '14 at 07:21
Yeah, that's nice. What did you do instead? – Günter Zöchbauer Sep 29 '14 at 07:22
Exactly as your function...just no 'return' statement ;-) – NullPumpkinException Sep 29 '14 at 10:15
Seems I misunderstood your comment ;-). Yeah - just the return was missing. – Günter Zöchbauer Sep 29 '14 at 10:16

score 1 · Answer 2 · edited Sep 29 '14 at 06:26

The problem is that your code returns a Future, and your test completes before the code in the Future has finished, so there's nothing to cause it to fail.

Check out the Asynchronous Tests section on the Dart site. There are methods like expectAsync that allow the future to be passed to the test framework so that it can wait for them to complete and handle the result correctly.

Here's an example (note the expect call is now inside the function passed to expectAsync)

test('callback is executed once', () {
  // wrap the callback of an asynchronous call with [expectAsync] if
  // the callback takes 0 arguments...
  var timer = Timer.run(expectAsync(() {
    int x = 2 + 3;
    expect(x, equals(5));
  }));
});

Dart Unit Test - Always passing

2 Answers2