Input validation is the act of ensuring data entering a system is correct and useful before relying on it for further processing. Think of it like a bouncer at an exclusive tech conference - if your data isn't on the list, it's not getting in.

How to use it in a sentence

"We can't launch yet - marketing forgot to add input validation on the user registration form, so now our database is full of test@test.com and bobby tables."

"Oops, looks like there was no input validation on that API endpoint - now we've got hackers pwning our production servers and mining Bitcoin."

If you actually want to learn more...

• Martin Fowler discusses the importance of contextual validation and considering the specific action being performed, rather than just generic "isValid" checks. Read more in his article on Contextual Validation.

• Fowler also touches on the challenges of testing when validation and other concerns are tightly coupled, making it harder to simulate and control in test environments. He dives deeper in Modern Mocking Tools and Black Magic.

• For a broader look at Fowler's thoughts on tools, testing, and software development practices, check out his tag archive on tools covering everything from API design to microservices.

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