This is about how to Mock Riverpod's Notifier and set its status

Question

This is how it is described in the official documentation.

class MyNotifier extends Notifier<int> {
  @override
  int build() => throw UnimplementedError();
}

// Your mock needs to subclass the Notifier base-class corresponding
// to whatever your notifier uses
class MyNotifierMock extends Notifier<int> with Mock implements MyNotifier {}

But I don't know how to use this. How can I set the status?

Answer 1

Maybe you can use Mock Notifier like this:

MyNotifier's state is int type state,

you can use Mock Notifier when you write test code about your riverPod Notifier codes,

please ref under these codes:

class MyNotifier extends Notifier<int> {
  @override
  int build() {
    return 0;
  }

  void increment() {
    state = state + 1;
  }
}

class MyNotifierMock extends Notifier<int> with Mock implements MyNotifier {
  @override
  int build() {
    return 0;
  }

  void increment() {
    state = state + 2;
  }
}

Answer 2

per the official docs

It is generally discouraged to mock Notifiers. Instead, you should likely introduce a level of abstraction in the logic of your Notifier, such that you can mock that abstraction. For instance, rather than mocking a Notifier, you could mock a "repository" that the Notifier uses to fetch data from.

The docs provide examples:

@riverpod
class MyNotifier extends _$MyNotifier {
  @override
  int build() => 123;
}
class MyNotifierMock with Mock implements MyNotifier {}

How can I set the status?

To set the initial state, you can override the Notifier's build, eg:

class MyNotifierMock with Mock implements MyNotifier {
final T? initialState;
const MyNotifierMock(this.initialState);
@override
      int build() => initialState ?? <SomeDefaultValue>;
}