dustinlessard-wf/stream_test_scheduler

stream_test_scheduler

Test if a stream emits elements at a certain time (window). It works similar to TestScheduler in RxJS, but it uses real time (milliseconds) instead of virtual time, since you can't fake time in Dart (see Irn's comment on stackoverflow). You can pass a maximum deviation to the matcher to specify a time window.

Usage

This example tests the function Stream delay(Stream input, Duration duration) (from stream_ext package) that time shifts elements on a stream input by duration. The relative time intervals between the values are preserved.

import 'dart:async';

import 'package:stream_ext/stream_ext.dart';
import 'package:stream_test_scheduler/stream_test_scheduler.dart';
import 'package:test/test.dart';

main() async {
  test('delay preserves relative time intervals between the values', () async {
    var scheduler = new TestScheduler();

    var source = scheduler.createStream(
        [onNext(150, 1), onNext(200, 2), onNext(230, 3), onCompleted(260)]);

    var result = await scheduler
        .startWithCreate(() => StreamExt.delay(source, ms(1000)));

    expect(
        result,
        equalsRecords([
          onNext(1150, 1),
          onNext(1200, 2),
          onNext(1230, 3),
          onCompleted(1260)
        ], maxDeviation: 20));
  });
}

I use a maximum deviation of 20 milliseconds in this example. But deviation varies. You might have to use a different maximum deviation value for another test or on another (faster/slower) system.

Features and bugs

Please file feature requests and bugs at the issue tracker.