test/stream_extensions_test.dart

// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE filevents.

import 'dart:async';

import 'package:async/async.dart';
import 'package:test/test.dart';

void main() {
  group('.slices', () {
    test('empty', () {
      expect(Stream.empty().slices(1).toList(), completion(equals([])));
    });

    test('with the same length as the iterable', () {
      expect(
          Stream.fromIterable([1, 2, 3]).slices(3).toList(),
          completion(equals([
            [1, 2, 3]
          ])));
    });

    test('with a longer length than the iterable', () {
      expect(
          Stream.fromIterable([1, 2, 3]).slices(5).toList(),
          completion(equals([
            [1, 2, 3]
          ])));
    });

    test('with a shorter length than the iterable', () {
      expect(
          Stream.fromIterable([1, 2, 3]).slices(2).toList(),
          completion(equals([
            [1, 2],
            [3]
          ])));
    });

    test('with length divisible by the iterable\'s', () {
      expect(
          Stream.fromIterable([1, 2, 3, 4]).slices(2).toList(),
          completion(equals([
            [1, 2],
            [3, 4]
          ])));
    });

    test('refuses negative length', () {
      expect(() => Stream.fromIterable([1]).slices(-1), throwsRangeError);
    });

    test('refuses length 0', () {
      expect(() => Stream.fromIterable([1]).slices(0), throwsRangeError);
    });
  });

  group('.firstOrNull', () {
    test('returns the first data event', () {
      expect(
          Stream.fromIterable([1, 2, 3, 4]).firstOrNull, completion(equals(1)));
    });

    test('returns the first error event', () {
      expect(Stream.error('oh no').firstOrNull, throwsA('oh no'));
    });

    test('returns null for an empty stream', () {
      expect(Stream.empty().firstOrNull, completion(isNull));
    });

    test('cancels the subscription after an event', () async {
      var isCancelled = false;
      var controller = StreamController<int>(onCancel: () {
        isCancelled = true;
      });
      controller.add(1);

      await expectLater(controller.stream.firstOrNull, completion(equals(1)));
      expect(isCancelled, isTrue);
    });

    test('cancels the subscription after an error', () async {
      var isCancelled = false;
      var controller = StreamController<int>(onCancel: () {
        isCancelled = true;
      });
      controller.addError('oh no');

      await expectLater(controller.stream.firstOrNull, throwsA('oh no'));
      expect(isCancelled, isTrue);
    });
  });
}