flutter_stasis_test

Test helpers for flutter_stasis.

---

Installation

dev_dependencies:
  flutter_stasis_test: ^1.0.0
  flutter_test:
    sdk: flutter

---

Why

Testing a StasisViewModel is straightforward — call a method, check the state. But writing the capture/assertion loop manually gets repetitive:

// Without helpers — repeated in every test file
final states = <MyState>[];
vm.stateListenable.addListener(() => states.add(vm.state));
await vm.load();
expect(states[0].isLoading, isTrue);
expect(states[1].projects, hasLength(3));

With flutter_stasis_test:

await assertStateSequence(
  listenable: vm.stateListenable,
  act: vm.load,
  expected: [
    (s) => s.isLoading,
    (s) => s.projects?.length == 3,
  ],
  includeInitial: false,
);

---

captureStates

Collects all state values emitted while act runs:

final states = await captureStates(
  listenable: vm.stateListenable,
  act: vm.load,
  includeInitial: true, // include the state before act runs (default: true)
);

expect(states, hasLength(3));       // initial + loading + success
expect(states[1].isLoading, isTrue);
expect(states[2].projects, isNotEmpty);

---

captureEvents

Collects all UiEvents emitted while act runs:

final events = await captureEvents(
  stream: vm.events,
  act: vm.save,
);

expect(events, [isA<ShowSnackBarEvent>(), isA<PopEvent>()]);

---

assertStateSequence

Captures states and asserts each one with a predicate. Fails with a descriptive message if the length or any predicate doesn't match:

await assertStateSequence(
  listenable: vm.stateListenable,
  act: vm.load,
  expected: [
    (s) => s.isLoading,
    (s) => s.projects?.length == 3,
  ],
  includeInitial: false,
);

Using equalsValue for simple equality:

await assertStateSequence(
  listenable: vm.stateListenable,
  act: vm.setFilter,
  expected: [
    equalsValue(ProjectsState(filter: ProjectFilter.active, ...)),
  ],
  includeInitial: false,
);

---

assertEventSequence

Same as assertStateSequence but for events:

await assertEventSequence(
  stream: vm.events,
  act: vm.onSavePressed,
  expected: [
    (e) => e is ShowSnackBarEvent && e.message == 'Saved',
    (e) => e is NavigateToEvent,
  ],
);

---

Full test example

import 'package:flutter_test/flutter_test.dart';
import 'package:flutter_stasis_test/flutter_stasis_test.dart';

void main() {
  late ProjectsViewModel vm;
  late MockGetProjectsUseCase mockUseCase;

  setUp(() {
    mockUseCase = MockGetProjectsUseCase();
    vm = ProjectsViewModel(mockUseCase);
  });

  tearDown(() => vm.dispose());

  test('load emits loading then success', () async {
    final fakeProjects = [Project(id: '1', name: 'Test')];
    when(() => mockUseCase.call()).thenAnswer(
      (_) async => Right(fakeProjects),
    );

    await assertStateSequence(
      listenable: vm.stateListenable,
      act: vm.load,
      expected: [
        (s) => s.isLoading,
        (s) => s.projects == fakeProjects,
      ],
      includeInitial: false,
    );
  });

  test('load emits error on failure', () async {
    when(() => mockUseCase.call()).thenAnswer(
      (_) async => Left(AppFailure('Network error')),
    );

    await assertStateSequence(
      listenable: vm.stateListenable,
      act: vm.load,
      expected: [
        (s) => s.isLoading,
        (s) => s.errorMessage == 'Network error',
      ],
      includeInitial: false,
    );
  });

  test('save emits snackbar event then navigates', () async {
    await assertEventSequence(
      stream: vm.events,
      act: vm.save,
      expected: [
        (e) => e is ShowSnackBarEvent,
        (e) => e is NavigateToEvent,
      ],
    );
  });
}

---

settle parameter

If your command involves microtasks or delayed work, use settle to wait before collecting:

await assertStateSequence(
  listenable: vm.stateListenable,
  act: vm.loadWithDebounce,
  expected: [...],
  settle: const Duration(milliseconds: 500),
);

---

License

MIT