Most of my career has been in banking, adtech and email infrastructure, where one flow runs through half a dozen systems before it is finished. A record comes in over an HTTP API, lands in Postgres or Mongo, gets pushed into Redis and triggers an email over SMTP that I then have to go and find in a mailbox over IMAP to know it arrived. I tested each of those hops with its own client. The glue between them was a pile of throwaway scripts that passed results along by hand.
So I built a tool that I always thought would be a useful addition to my own stack – one workbench where the whole flow is a single test. Each step is a probe you compose in a UI editor, steps stack into a chain, where an extractor pulls a value out of one response and feeds it into the next request (or an assertion). When the logic gets past what an extractor can do, there is JavaScript on a GraalVM engine to fall back to. Chains can be grouped into suites.
A run comes out as a JUnit report (or evidence JSON) and everything can be easily integrated with a CI/CD pipeline (I am actually testing the product using it via Github Actions; writeup pending).
It covers 16 protocols, from HTTP and SMTP to SMB and Kerberos, every one written against the RFC instead of wrapping a library. A library only gives you a well-formed request. The cases I often care about are the malformed packet and the behavior of the server when I send one. Because I write each protocol myself, the same workbench can fuzz with broken input or sit in a SOCKS5 proxy between client and server and change what goes past.
The part of that proxy I enjoy using most is the mocking. It can stand in for the server and return a response that is not built yet, so I can author and run a test against an endpoint before it exists (a canned response, or a scripted one; a chain flips a mock rule set on just for its own run). It is not HTTP-only (SMTP, IMAP, DNS, the STOMP broker and the databases mock too), though a database mocks a narrow auth error rather than a full result set.
The agent side came later. The workbench exposes an MCP server and a full toolbox, so an agent can create tests (under my supervision) as well, run a chain or a suite and get a structured result back, staying inside exactly the scope I authored.
The application is a closed-source desktop app called VirtuProbe Studio. The free tier covers HTTP, DNS and SMTP.
I am 100% interested in hearing your feedback – and super happy for every bug report that lands in my youtrack
Source: r/SideProject · by /u/GesHusDer