Gap Between Documentation and Actual Implementation

Robustness principle

If you have machine-readable specifications for our message formats, we should be able to verify these properties by analyzing the new specification relative to the old spec. A tough problem arises that we need to address when applying the Robustness Principle, though. There may be a gap between what we say our service accepts and what it really accepts.

JSON payload example

For instance, suppose a service takes JSON payloads with a url field. We discover that the input is not validated as a URL, but just received as a string and stored in the database as a string. We want to add some validation to check that the value is a legitimate URL, maybe with a regular expression. Bad news: the service now ...