Recipe for funtion call verification within stream matchers

[raveesh-me]

Code that I want to test:

 final cachedResult = cacheBox.get(uri);
    if (cachedResult != null)
      controller.add(SWREvent(
        eventStatus: SWREventStatus.cacheResponse,
        data: cachedResult,
        swrMessage: 'returning the cached data first',
      ));

    /// make the network call
    final response = await this.getUri(uri,
        options: options,
        cancelToken: cancelToken,
        onReceiveProgress: onReceiveProgress);

    /// if our response is a failure, we should invalidate cache and
    /// return the error response
    if (response.statusCode != 200) {
      if (cachedResult != null) cacheBox.delete(uri);
      controller.add(SWREvent(
        eventStatus: SWREventStatus.error,
        data: response.data,
        dioResponse: response,
        swrMessage: response.statusMessage,
      ));
      controller.close();
      return;
    }

    /// if our cached data is up to date with remote, we should
    /// close the streamcontroller and return.
    if (cachedResult != null && response.data == cachedResult) {
      controller.close();
      return;
    }

    /// finally, we should update the cache anyways, and push the result to the
    /// stream and close the controller
    cacheBox.put(uri, response.data);
    controller.add(SWREvent(
        data: response.data,
        eventStatus: SWREventStatus.networkResponse,
        swrMessage: null));
    controller.close();
    return;

My test:

test('''WHEN mockbox returns null
    GET only networkResponse
    AND Box put method called''', () async {
      MockBox mockBox = MockBox();
      Stream sWRStream = Dio().getSWRUri(
        Uri.parse(REQUEST_URI),
        mockBox,
      );
      expect(
        sWRStream,
        emitsInOrder([
          isA<SWREvent>().having(
            (swrEvent) => swrEvent.eventStatus,
            'only network response is pushed',
            SWREventStatus.networkResponse,
          ),
          emitsDone,
        ]),
      );
    });
  });

Purpose

I want to verify whether the put() has been called in the stream, and can not find any example where I can add the verify method for this use case.

Preferred Solution

I would like to have something like this...

expect(
        sWRStream,
        emitsInOrder([
          isA<SWREvent>().having(
            (swrEvent) => swrEvent.eventStatus,
            'only network response is pushed',
            SWREventStatus.networkResponse,
          ),
          emitsDone.havingVerified(MockBox.put(any, any).called(1), 'put method was called on box once'),
        ]),
      );

[srawlins]

Thanks for the question. I think I partially understand it :). FIrst, when you say "I want to verify whether the put() has been called in the stream," I'm a little lost. This is the first mention of a method called put. It's not in the Code you want to test, nor in the test.

Second, "has been called in the stream" is not a concept I'm comfortable with sticking to. A stream is just a sequence of objects, it is not a... sequence of actions or of method calls... I'll hazard a guess that you want to verify that, in the process of listening to the stream, and reading objects out of it, mockBox.put was called.

If this is the case, why not just use the standard verify API immediately after verifying the stream's contents with emitsInOrder? Are the Stream matchers asynchronous as well? I think expectLater may help here...

[raveesh-me]

@srawlins thanks for the comment. :)

I want to verify that as a side effect, the local database, in this case hive, is receiving a write request, which is something I want to be sure about in this unit.

mockBox.put is Box.put from Hive, which is our local database for now.
I have also updated the reference code, I had initially missed including it there.

you are right about streams, I also want to stick to thinking of streams as a series of events. I just want to verify if whether a method for a side effect has been called from when the execution started to when the stream was closed.

problem with using the standard verify() is, that I can not await the expect() in with StreamMatcher. This means the verify will be executed before stream has closed.

I would be thankful if someone could show me how to put a verify inside an expectLater.