public void CreateANewAccount_AccoutExists_ReturnAccountExist() { // Arrange var unitUnderTest = this.CreateAccountAPI(); string id = "A123456789"; subAccountRepo.IsExist(Arg.Any <string>()).Returns(true); string expected = "此身分證已建立過帳號"; // Act var result = unitUnderTest.CreateANewAccount( id); // Assert Assert.Equal(expected, result); subAccountRepo.DidNotReceive().Create(Arg.Any <string>()); }