public void ShouldAddCustomerLogin(int customerId)
{
// arrange
var customer = new Mock <ICustomer>();
_context.Customers.Setup(x => x.GetById(100)).Returns(customer.Object);
ILoginInfo addedLogin = null;
customer.Setup(x => x.AddLogin(It.IsAny <ILoginInfo>())).Callback((ILoginInfo i) => addedLogin = i);
// act
_service.AddCustomerLogin(customerId, "provider", "login");
// assert
addedLogin.ShouldNotBeNull();
addedLogin.ProviderName.ShouldBe("provider");
addedLogin.LoginKey.ShouldBe("login");
_context.Customers.Verify(x => x.Update(customer.Object));
}