- System changes speed: If the system responds slower or faster, those using it will respond to that. Improving your performance can have negative impacts on the consumers of your system, if the user expects a certain speed of response.
- Systems inherent fragility changes: If the system has more or less availability this will change interaction. Expectations will rise (or fall), so might volume!
So, next time someone says “there’s no functional change”, as a tester remember that there is more to a system than the functionality it contains, its behaviour has a profound effect on its stakeholders.
Remember, if you convert your teapot to be made from chocolate, its function is the same but it’s behaviour is pretty different!