---
title: "How to Test Any API Without Documentation"
url: https://daily.dev/posts/how-to-test-any-api-without-documentation-vjubk1nzv
source_url: https://www.youtube.com/watch?v=SvZhlATmA3Y
type: video:youtube
source: "Automation Testing with Joe Colantonio"
published: 2026-06-30T11:36:56.582Z
updated: 2026-06-30T11:37:17.007Z
tags: ["open-source", "testing"]
reading_time: 23
upvotes: 1
comments: 1
language: en
---

> ## Documentation Index
> Fetch the complete documentation index at: https://daily.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# How to Test Any API Without Documentation

**[Automation Testing with Joe Colantonio](https://daily.dev/sources/joecolantonio)** · 23 min read · 1 upvotes · 1 comments

## Summary

A podcast interview with Ludis, a 20-year software testing veteran who built Rentgen, a free open-source API testing tool. The conversation covers how to discover undocumented internal APIs using browser DevTools, and how Rentgen automates the tedious parts of API testing — edge cases, boundary tests, security header checks, and basic performance insights — by taking a single API request, mapping its fields, and auto-generating dozens of test cases. The tool is fully local (no cloud calls), complements existing Postman/Playwright automation rather than replacing it, and is intended as a first-pass sanity check before deeper automation begins. CI/CD integration is on the roadmap.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://www.youtube.com/watch?v=SvZhlATmA3Y>

## Community discussion

Top comments from developers on daily.dev.

**@liudasjan** · 0 upvotes

> One API request can reveal a lot more than most teams expect. That’s the idea behind Rentgen—start with real traffic, then automatically explore everything around it before writing a single test.

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---

Tags: [#open-source](https://daily.dev/tags/open-source), [#testing](https://daily.dev/tags/testing)

[View this post on daily.dev](https://daily.dev/posts/how-to-test-any-api-without-documentation-vjubk1nzv)