public void Save_invalid_bird_should_throw_exception()
{
var bird = new Bird("Tree sparrow");
_validatorMock.IsValid(Arg.Any <Bird>()).Returns(false);
Action a = () => _sut.Save(bird);
a.ShouldThrow <ArgumentException>();
_repositoryMock.DidNotReceive().SaveOrUpdate(Arg.Any <Bird>());
}