How to test code that uses DateTime.now in Flutter?

If you use the clock package for code depending on DateTime.now() you can easily mock it.

I don't think there is a good way without a wrapper around DateTime.now() licke the clock package provides.

As mentioned here: https://stackoverflow.com/a/63073876/2235274 implement extension on DateTime.

extension CustomizableDateTime on DateTime {  static DateTime _customTime;  static DateTime get current {    return _customTime ?? DateTime.now();  }  static set customTime(DateTime customTime) {    _customTime = customTime;  }}

Then just use CustomizableDateTime.current in the production code. You can modify the returned value in tests like that: CustomizableDateTime.customTime = DateTime.parse("1969-07-20 20:18:04");. There is no need to use third party libraries.

As Günther said, the clock package, maintained by the Dart team, provides a very neat way to achieve this.

Normal usage:

import 'package:clock/clock.dart';void main() {  // prints current date and time  print(clock.now());}

Overriding the current time:

import 'package:clock/clock.dart';void main() {  withClock(    Clock.fixed(DateTime(2000)),    () {      // always prints 2000-01-01 00:00:00.      print(clock.now());    },  );}

I wrote about this in more detail on my blog.

For widget tests, you need to wrap pumpWidget, pump and expect in the withClock callback.