public void AddCardToWallet(int wallet, string cardName, double interest, double balance) { sut.People.Add(user1Mock.Object); sut.People.Add(user2Mock.Object); sut.AddCardToWallet(username1, wallet, cardName, interest, balance); user1Mock.Verify(x => x.AddCard(wallet, cardName, interest, balance), Times.Once); user2Mock.Verify(x => x.AddCard(wallet, cardName, interest, balance), Times.Never); }