I recently got a meme about my own tool. Honestly, that’s probably the best kind of feedback you can get. If people are joking about it, it means the idea landed and the tool is starting to resonate.
So let me clear up something before this turns into another “Postman vs X” discussion.
Rentgen does not replace Postman. It never will. And that’s intentional.
Postman is great at what it does: scripted tests, assertions, collections, CI workflows, long-lived test suites. If you live there, keep using it. Rentgen is not competing in that space. Rentgen exists before Postman. Before CI/CD. Before full automation.
The moment Rentgen is designed for is very simple. You’ve just built an API endpoint. You have a cURL. You want a fast reality check. Not a test framework. Not scripts. Not assertions. You just want to see how the API behaves when inputs are not perfect.
Most developers use Postman as an API client. Paste a request, send it once, see a response, move on. No negative cases. No edge cases. Not because people are lazy, but because the first “proper” testing step already feels heavy.
That’s how APIs get handed over with the classic line: “I tested it. It works.”
Rentgen is for that gap nobody likes to talk about. You paste one cURL and run it. Rentgen expands it into a messy, realistic set of requests: missing fields, wrong types, boundary values, enum casing issues, whitespace, malformed payloads. The boring stuff that causes real production bugs.
There are no assertions by design. Rentgen isn’t trying to prove your API is correct. It’s trying to show how it behaves when reality hits. 2xx–3xx means acceptable behaviour. 4xx means the API handled bad input without panicking. 5xx is a signal something is wrong.
This is not a test suite. It’s a reality check.
Run Rentgen first. Fix the obvious issues. Then move to Postman, CI, and proper automated tests. Developers look more professional, testers don’t waste time on low-hanging bugs, and fewer surprises reach production.
So no, this isn’t about replacing tools. It’s about putting the right tool in the right moment. If a meme helped explain that, I’ll happily take it.
Top comments (3)
Read more at: rentgen.io
Great post - thanks for the insight!
Thanks! Glad it resonated 👍