CODEWITHSUNDEEP
dartflutter-testrxdart
Juan Cruz Soler
Juan Cruz Soler

Reputation: 8254

Test stream with wrapped array

I'm trying to test that the function emitArray emits a Response.Success an its value is ['test'].
If I emit a List<String> everything works as expected, but once I wrap the result list in a Response<List<String>> the test fails.

The result is emitted, but it fails when comparing with the expected result.
I'm wondering if it's related to the implementation of == in Response.Success, I'm using the default implementation that the IDE provides.

This is not the real code I have, it's just a simple example that is easier to understand to try to identify the issue.

This is my class to test:

class ListResponse {
  final _array = BehaviorSubject<Response<List<String>>>();

  Stream<Response<List<String>>> get array => _array.stream;

  Future<void> emitArray() async {
    _array.add(Response.success(['test']));
  }

  void dispose() {
    _array.close();
  }
}

This is my test:

void main() {
  ListResponse underTest;
  setUp(() {
    underTest = ListResponse();
  });

  test('It should emit array', () {
    final array = Response.success(['test']);

    expect(
      underTest.array,
      emitsInOrder([
        array,
        emitsDone,
      ]),
    );

    underTest.emitArray();

    underTest.dispose();
  });
}

This is the error it throws:

Expected: should do the following in order:
          • emit an event that SuccessResponse<List<String>>:<SuccessResponse{value: [test]}>
          • be done
  Actual: <Instance of 'BehaviorSubject<Response<List<String>>>'>
   Which: emitted • SuccessResponse{value: [test]}
                  x Stream closed.
            which didn't emit an event that SuccessResponse<List<String>>:<SuccessResponse{value: [test]}>

This is the Response class

class Response<T> {
  Response._();

  factory Response.success(T value) = SuccessResponse<T>;
  factory Response.error(Exception error) = ErrorResponse<T>;
}

class ErrorResponse<T> extends Response<T> {
  ErrorResponse(this.error): super._();

  final Exception error;

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
          other is ErrorResponse &&
              runtimeType == other.runtimeType &&
              error == other.error;

  @override
  int get hashCode => error.hashCode;

  @override
  String toString() {
    return 'ErrorResponse{error: $error}';
  }
}

class SuccessResponse<T> extends Response<T> {
  SuccessResponse(this.value): super._();

  final T value;

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
          other is SuccessResponse &&
              runtimeType == other.runtimeType &&
              value == other.value;

  @override
  int get hashCode => value.hashCode;

  @override
  String toString() {
    return 'SuccessResponse{value: $value}';
  }
}

Upvotes: 2

Views: 240

Answers (1)

Styx
Styx

Reputation: 10076

I'm wondering if it's related to the implementation of == in Response.Success

Exactly. This particular test is failing because you can't compare Lists with ==:

abstract class List<E> implements EfficientLengthIterable<E> {
  ...
  /**
  * Whether this list is equal to [other].
  *
  * Lists are, by default, only equal to themselves.
  * Even if [other] is also a list, the equality comparison
  * does not compare the elements of the two lists.
  */
 bool operator ==(Object other);
}

As a workaround you can change the implementation to compare objects' string representations instead:

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is SuccessResponse &&
          runtimeType == other.runtimeType &&
          value.toString() == other.value.toString();

Interestingly, passing unwrapped List<String>s objects passes test. That happens because StreamMatcher uses equals() from matcher package to match events, and equals() can match lists and maps. It first tries to match objects with ==, then checks whether they are Iterable/Set/Map (and deep matches them recursively), and then reports mismatch error.

Upvotes: 1

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