public async Task GivenAnAggregateWithChangesThenSaveIsCalledAsync()
{
var repository = new Mock <IRepository <SerializableAggregateRoot> >();
var aggregate = new SerializableAggregateRoot();
await aggregate.SaveAsync(repository.Object);
repository.Verify(
repo => repo.SaveAsync(
It.IsAny <SerializableAggregateRoot>(),
It.IsAny <CancellationToken?>()),
Times.Once);
}