API Spector a new Open Source API Testing Tool

TLDR; API Spector is a new free HTTP and WebSocket Testing Tool.

New Tool for HTTP Testing

I haven’t added this to the API Challenges site yet but I spent a bit of time looking at the API Spector tool.

A new Open Source REST and WebSocket testing tool.

Instructions for getting it running are in the read me. It’s pretty good.

• https://github.com/testsmith-io/api-spector

Docs are here:

• https://testsmith-io.github.io/api-spector

API Spector Features

It is completely free and open source, and stores all requests to files so they can be version controlled - just like Bruno.

It has built in Git integration, which I wasn’t expecting.

And it has proxy support, which I always use because I like to see the actual requests and responses being sent.

API Spector has a lot of functionality.

• Importing from Postman, Insomnia, OpenAPI or Bruno.
• Sending requests over HTTP or web sockets
• Supports request variables by adding them in the Pre-request Script - not quite as easy as a GUI interface but still fine

The Tree view in the response body view makes it easy to add assertions into the Post-response script section and convert requests into a more repeatable set of assertions.

I normally don’t use this type of feature because it is more a pain than a benefit but… the UI makes this easy to add, so I can imagine making more use of it.

The tool has no ’limits’ in here so you can run folders of requests, add as many ’tests’ as you want.

And there are features I haven’t seen in other free tools:

• setting it up to mock requests and create a mock server
• contract based testing

The contract based testing goes beyond a simple set of assertions in the post script and is schema based.

You can also use it to generate basic test code from collections as well.

I need to do a longer session to use it, and then create a write up for API Challenges, but I’m pretty impressed.

API Spector Competition

If you read this prior to May 9th 2026 then Roy de Kleijn (the tool’s author) is running a competition - write about the tool, and possibly win one of 5 Amazon vouchers.

• Learn about the competition here

This post will not be entered into the competition.