public async Task AddEntry_When_Duplicate_Entry_Throws_exception()
{
//arrange
var repository = Substitute.For <IPhoneBookRepository>();
repository.GetById("Test").Returns(new PhoneBookEntry());
var phoneBookService = new PhoneBookService(repository);
//act + assert
await Assert.ThrowsExceptionAsync <ApplicationException>(() =>
phoneBookService.AddEntry(new PhoneBookEntry
{
Name = "Test",
PhoneNumber = "123"
}));
}