Is there a way to fake DateTime.now() in a Flutter test? - testing

Question

I can pass in a time to my widget, but my widget is supposed to be instantiating the time in itself, not receiving a DateTime from a parent widget.

Answer 1

The clock package: https://pub.dartlang.org/documentation/clock/latest/clock/clock-library.html lets you inject a fake clock into the test.

Answer 2

extension CustomizableDateTime on DateTime {
static DateTime customTime;
static DateTime get current {
if (customTime != null)
return customTime;
else
return DateTime.now();
}
}
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.

Answer 3

As Mary said, a very neat way is to use the clock package, which maintained by the Dart team.
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.
Just note that for widget tests, you need to wrap pumpWidget, pump and expect in the withClock callback - only wrapping pumpWidget does not work.