public void AddUpdate_Updates()
{
target.AddUpdate("TestUserName", new PaymentMethod { Id = "address1", CardholderName = "TestFName" });
target.AddUpdate("TestUserName", new PaymentMethod { Id = "address1", CardholderName = "TestFirstName" });
Assert.AreEqual(1, target.GetAll("TestUserName").Count());
Assert.AreEqual("TestFirstName", target.GetAll("TestUserName").First().CardholderName);
}