value_listenable_test

Assists in testing ValueListenable objects (ex: ValueNotifier).

install

Added in your pubspec.yaml as dev dependency:

dev_dependencies:
  value_listenable_test: any

Unit test with emitValues and valueListenableTest

Listen the emits of ValueListenable:

 test('valueListenable Matcher', () {
     final counter = ValueNotifier(0);
     expect(counter, emitValues([2, 3, 5]));
     counter.value = 2;
     counter.value = 3;
     counter.value = 5;
   });

Also, you can use the test abstraction called valueListenableTest:

valueListenableTest<Counter>(
  'Counter emits [1] when update method is called',
  build: () => Counter(),
  act: (notifier) => notifier.update(1),
  expect: () => [1],
);

Mock

It's easy, just extend the MockValueListenable:

class MockCounter extends MockValueListenable<int> {}

To notify the listeners with a new value call the [callListeners] method.

final counter = MockCounter();
counter.addListener(() => print(counter.value)); // 50
when(() => counter.value).thenReturn(50);
print(counter.value); // 50
counter.callListeners();

Stub the value

Creates a stub response for the addListener method on a valueListenable. The valueListenable will have each value (in order) after theinput is called. Optionally provide an initialValue to stub the value of the valueListenable, or also optionally provide a delay between the values change.

// Create a mock instance
final counter = CounterMock();

// Stub the value
whenListen(
  counter,
  input: counter.increment,
  initialValue: 0,
  values: [1, 2, 3],
);

// Assert that the initial value is correct.
expect(counter.value, 0);

// Verifies values after to call increment
valueListenableTest<Counter>(
  'value = [1, 2, 3] when increment is called',
  build: () => counter,
  act: (notifier) => notifier.increment(),
  expect: () => [1, 2, 3],
);

Note: When setting the initialValue the listeners are never called, then emitValues and valueListenableTest methods never must expect that.

That`s it!