# TestWidgetsFlutterBinding.clock change

> The Clock implementation now comes from package:clock.




:::important
These breaking change docs are accurate, as of the release
under which they are published. Over time, the
workarounds described here might become inaccurate.
We don't, in general, keep these breaking change docs up
to date as of each release.

The [breaking change index file](/release/breaking-changes)
lists the docs created for each release.
:::


## Summary

The `TestWidgetsFlutterBinding.clock` now comes from
`package:clock` and not `package:quiver`.

## Context

The `flutter_test` package is removing its dependency on
the heavier weight `quiver` package in favor of a dependency
on two more targeted and lighter weight packages,
`clock` and `fake_async`.

This can affect user code which grabs the clock from a
`TestWidgetsFlutterBinding` and passes that to an API
that expects a `Clock` from `package:quiver`,
for example some code like this:

```dart
testWidgets('some test', (WidgetTester tester) {
  someApiThatWantsAQuiverClock(tester.binding.clock);
});
```

## Migration guide

The error you might see after this change looks something like this:

```plaintext
Error: The argument type 'Clock/*1*/' can't be assigned to the parameter type 'Clock/*2*/'.
 - 'Clock/*1*/' is from 'package:clock/src/clock.dart' ('<pub-cache>/clock/lib/src/clock.dart').
 - 'Clock/*2*/' is from 'package:quiver/time.dart' ('<pub-cache>/quiver/lib/time.dart').
```

### Option #1: Create a package:quiver Clock from a package:clock Clock

The easiest migration is to create a `package:quiver` clock from the
`package:clock` clock, which can be done by passing the `.now` function
tearoff to the `Clock` constructor:

Code before migration:

```dart
testWidgets('some test', (WidgetTester tester) {
  someApiThatWantsAQuiverClock(tester.binding.clock);
});
```

Code after migration:

```dart
testWidgets('some test', (WidgetTester tester) {
  someApiThatWantsAQuiverClock(Clock(tester.binding.clock.now));
});
```

### Option #2: Change the api to accept a package:clock Clock

If you own the api you are calling,
you may want to change it to accept a `Clock`
from `package:clock`.
This is a judgement call based on how many places are
calling this API with something other than a clock
retrieved from a `TestWidgetsFlutterBinding`.

If you go this route, your call sites that are passing
`tester.binding.clock` won't need to be modified,
but other call sites will.

### Option #3: Change the API to accept a `DateTime function()`

If you only use the `Clock` for its `now` function,
and you control the API, then you can also change it
to accept that function directly instead of a `Clock`.
This makes it easily callable with either type of `Clock`,
by passing a tearoff of the `now` method from either type of clock:

Calling code before migration:

```dart
testWidgets('some test', (WidgetTester tester) {
  someApiThatWantsAQuiverClock(tester.binding.clock);
});
```

Calling code after migration:

```dart
testWidgets('some test', (WidgetTester tester) {
  modifiedApiThatTakesANowFunction(tester.binding.clock.now);
});
```

## Timeline

Landed in version: 1.18.0<br>
In stable release: 1.20

## References

API documentation:

* [`TestWidgetsFlutterBinding`][]

Relevant PRs:

* [PR 54125][]: remove flutter_test quiver dep,
  use fake_async and clock instead

[`TestWidgetsFlutterBinding`]: https://api.flutter.dev/flutter/flutter_test/TestWidgetsFlutterBinding-class.html
[PR 54125]: https://github.com/flutter/flutter/pull/54125