public void Test_AuditChangeOfAddress_OutputStringContainsCustomerIdOldAddressAndNewAddress()
{
//arrange
int id = 1;
string oldAddress = "5 Bar Street, Leeds";
string newAddress = "New Address";
Customer customer = new Customer(id, oldAddress);
AuditingSystem system = new AuditingSystem();
//act
string actualValue = system.AuditChangeOfAddress(customer, oldAddress, newAddress);
//assert
StringAssert.Contains(customer.Id.ToString(), actualValue);
StringAssert.Contains(oldAddress, actualValue);
StringAssert.Contains(newAddress, actualValue);
}