pkgs/stream_transform/test/throttle_test.dart

// Copyright (c) 2017, 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 file.

import 'dart:async';

import 'package:fake_async/fake_async.dart';
import 'package:stream_transform/stream_transform.dart';
import 'package:test/test.dart';

import 'utils.dart';

void main() {
  for (var streamType in streamTypes) {
    group('Stream type [$streamType]', () {
      late StreamController<int> values;
      late List<int> emittedValues;
      late bool valuesCanceled;
      late bool isDone;
      late Stream<int> transformed;
      late StreamSubscription<int> subscription;

      group('throttle - trailing: false', () {
        setUp(() async {
          valuesCanceled = false;
          values = createController(streamType)
            ..onCancel = () {
              valuesCanceled = true;
            };
          emittedValues = [];
          isDone = false;
          transformed = values.stream.throttle(const Duration(milliseconds: 5));
        });

        void listen() {
          subscription = transformed.listen(emittedValues.add, onDone: () {
            isDone = true;
          });
        }

        test('cancels values', () async {
          listen();
          await subscription.cancel();
          expect(valuesCanceled, true);
        });

        test('swallows values that come faster than duration', () {
          fakeAsync((async) {
            listen();
            values
              ..add(1)
              ..add(2)
              ..close();
            async.elapse(const Duration(milliseconds: 6));
            expect(emittedValues, [1]);
          });
        });

        test('outputs multiple values spaced further than duration', () {
          fakeAsync((async) {
            listen();
            values.add(1);
            async.elapse(const Duration(milliseconds: 6));
            values.add(2);
            async.elapse(const Duration(milliseconds: 6));
            expect(emittedValues, [1, 2]);
            async.elapse(const Duration(milliseconds: 6));
          });
        });

        test('closes output immediately', () {
          fakeAsync((async) {
            listen();
            values.add(1);
            async.elapse(const Duration(milliseconds: 6));
            values
              ..add(2)
              ..close();
            async.flushMicrotasks();
            expect(isDone, true);
          });
        });

        if (streamType == 'broadcast') {
          test('multiple listeners all get values', () {
            fakeAsync((async) {
              listen();
              var otherValues = <int>[];
              transformed.listen(otherValues.add);
              values.add(1);
              async.flushMicrotasks();
              expect(emittedValues, [1]);
              expect(otherValues, [1]);
            });
          });
        }
      });

      group('throttle - trailing: true', () {
        setUp(() async {
          valuesCanceled = false;
          values = createController(streamType)
            ..onCancel = () {
              valuesCanceled = true;
            };
          emittedValues = [];
          isDone = false;
          transformed = values.stream
              .throttle(const Duration(milliseconds: 5), trailing: true);
        });
        void listen() {
          subscription = transformed.listen(emittedValues.add, onDone: () {
            isDone = true;
          });
        }

        test('emits both first and last in a period', () {
          fakeAsync((async) {
            listen();
            values
              ..add(1)
              ..add(2)
              ..close();
            async.elapse(const Duration(milliseconds: 6));
            expect(emittedValues, [1, 2]);
          });
        });

        test('swallows values that are not the latest in a period', () {
          fakeAsync((async) {
            listen();
            values
              ..add(1)
              ..add(2)
              ..add(3)
              ..close();
            async.elapse(const Duration(milliseconds: 6));
            expect(emittedValues, [1, 3]);
          });
        });

        test('waits to output the last value even if the stream closes',
            () async {
          fakeAsync((async) {
            listen();
            values
              ..add(1)
              ..add(2)
              ..close();
            async.flushMicrotasks();
            expect(isDone, false);
            expect(emittedValues, [1],
                reason: 'Should not be emitted until after duration');
            async.elapse(const Duration(milliseconds: 6));
            expect(emittedValues, [1, 2]);
            expect(isDone, true);
            async.elapse(const Duration(milliseconds: 6));
          });
        });

        test('closes immediately if there is no pending value', () {
          fakeAsync((async) {
            listen();
            values
              ..add(1)
              ..close();
            async.flushMicrotasks();
            expect(isDone, true);
          });
        });

        if (streamType == 'broadcast') {
          test('multiple listeners all get values', () {
            fakeAsync((async) {
              listen();
              var otherValues = <int>[];
              transformed.listen(otherValues.add);
              values
                ..add(1)
                ..add(2);
              async.flushMicrotasks();
              expect(emittedValues, [1]);
              expect(otherValues, [1]);
              async.elapse(const Duration(milliseconds: 6));
              expect(emittedValues, [1, 2]);
              expect(otherValues, [1, 2]);
            });
          });
        }
      });
    });
  }
}