fake_async

This package provides a FakeAsync class, which makes it easy to deterministically test code that uses asynchronous features like Futures, Streams, Timers, and microtasks. It creates an environment in which the user can explicitly control Dart's notion of the "current time". When the time is advanced, FakeAsync fires all asynchronous events that are scheduled for that time period without actually needing the test to wait for real time to elapse.

For example:

import 'dart:async';
                
                import 'package:fake_async/fake_async.dart';
                import 'package:test/test.dart';
                
                void main() {
                  test("Future.timeout() throws an error once the timeout is up", () {
                    // Any code run within [fakeAsync] is run within the context of the
                    // [FakeAsync] object passed to the callback.
                    fakeAsync((async) {
                      // All asynchronous features that rely on timing are automatically
                      // controlled by [fakeAsync].
                      expect(Completer().future.timeout(Duration(seconds: 5)),
                          throwsA(isA<TimeoutException>()));
                
                      // This will cause the timeout above to fire immediately, without waiting
                      // 5 seconds of real time.
                      async.elapse(Duration(seconds: 5));
                    });
                  });
                }
                

Integration With clock

FakeAsync can't control the time reported by DateTime.now() or by the Stopwatch class, since they're not part of dart:async. However, if you create them using the clock package's clock.now() or clock.stopwatch() functions, FakeAsync will automatically override them to use the same notion of time as dart:async classes.

1.3.3

• Make the zone create*Timer and scheduleMicrotask be responsible for running callbacks in the zone they're scheduled in, matching (new) standard zone behavior. (The Timer constructors and top-level scheduleMicrotask used to bind their callback, but now only registers it, leaving the zone to run in the correct zone and handle errors.)
• Make periodic timers increment their tick by more than one if elapseBlocking advanced time past multiple ticks.

1.3.2

• Require Dart 3.3
• Fix bug where a flushTimers or elapse call from within the callback of a periodic timer would immediately invoke the same timer.
• Move to dart-lang/test monorepo.

1.3.1

• Populate the pubspec repository field.

1.3.0

• FakeTimer.tick will return a value instead of throwing.
• FakeAsync.includeTimerStackTrace allows controlling whether timers created with a FakeAsync will include a creation Stack Trace.

1.2.0

• Stable release for null safety.

1.2.0-nullsafety.3

• Update SDK constraints to >=2.12.0-0 <3.0.0 based on beta release guidelines.

1.2.0-nullsafety.2

• Allow prerelease versions of the 2.12 sdk.

1.2.0-nullsafety.1

• Allow 2.10 stable and 2.11.0 dev SDK versions.

1.2.0-nullsafety

Pre-release for the null safety migration of this package.

Note that 1.2.0 may not be the final stable null safety release version, we reserve the right to release it as a 2.0.0 breaking change.

This release will be pinned to only allow pre-release sdk versions starting from 2.10.0-0.

1.1.0

• Exposed the FakeTimer class as a public class.
• Added FakeAsync.pendingTimers which gives access to all pending timers at the time of the call.

1.0.2

• Update min SDK to 2.2.0

1.0.1

• Update to lowercase Dart core library constants.
• Fix use of deprecated isInstanceOf matcher.

1.0.0

This release contains the FakeAsync class that was defined in quiver. It's backwards-compatible with both the quiver version and the old version of the fake_async package.

New Features

• A top-level fakeAsync() function was added that encapsulates new FakeAsync().run(...).

New Features Relative to quiver

• FakeAsync.elapsed returns the total amount of fake time elapsed since the FakeAsync instance was created.

• new FakeAsync() now takes an initialTime argument that sets the default time for clocks created with FakeAsync.getClock(), and for the clock package's top-level clock variable.

New Features Relative to fake_async 0.1

• FakeAsync.periodicTimerCount, FakeAsync.nonPeriodicTimerCount, and FakeAsync.microtaskCount provide visibility into the events scheduled within FakeAsync.run().

• FakeAsync.getClock() provides access to fully-featured Clock objects based on FakeAsync's elapsed time.

• FakeAsync.flushMicrotasks() empties the microtask queue without elapsing any time or running any timers.

• FakeAsync.flushTimers() runs all microtasks and timers until there are no more scheduled.

0.1.2

• Integrate with the clock package.