public static void AddOrUpdateAddress_UpdatesAddress(
            Address existingAddress,
            AddressModel newOrUpdatedAddress,
            ContactDetailsService service)
        {
            existingAddress.Should().NotBeNull();
            newOrUpdatedAddress.Should().NotBeNull();

            var expected = new Address
            {
                Id       = existingAddress.Id,
                Line1    = newOrUpdatedAddress.Line1,
                Line2    = newOrUpdatedAddress.Line2,
                Line3    = newOrUpdatedAddress.Line3,
                Line4    = newOrUpdatedAddress.Line4,
                Line5    = newOrUpdatedAddress.Line5,
                Town     = newOrUpdatedAddress.Town,
                County   = newOrUpdatedAddress.County,
                Postcode = newOrUpdatedAddress.Postcode,
                Country  = newOrUpdatedAddress.Country,
            };

            var result = service.AddOrUpdateAddress(existingAddress, newOrUpdatedAddress);

            result.Should().BeEquivalentTo(expected);
        }
        public static void AddOrUpdateAddress_NullExistingAddress_NullNewAddress(
            ContactDetailsService service)
        {
            var result = service.AddOrUpdateAddress(null, null);

            result.Should().BeNull();
        }
        public static void AddOrUpdateAddress_NullNewAddress(
            Address existingAddress,
            ContactDetailsService service)
        {
            existingAddress.Should().NotBeNull();

            var result = service.AddOrUpdateAddress(existingAddress, null);

            result.Should().BeEquivalentTo(existingAddress);
        }