fizz-mbt

fizz-mbt is a skill for Claude Code, Codex from fizzbee-io/fizzbee. It costs 77 tokens per session (2,473 once invoked), scanned A, original, Apache-2.0.

A model-based testing workflow that turns a verified FizzBee state model into test sequences for a real software system. Model-based testing checks system behavior by exploring actions and state changes described in a model.

In plain words
What is it for?
Use it with a .fizz specification to generate and run tests against TypeScript or Playwright interfaces, Go services, Rust libraries, or Java applications.
Why use it?
It can explore many ordered and concurrent action sequences that are easy to miss in hand-written tests. The generated sequences run against the real application through an adapter.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/fizzbee-io/fizzbee/fizz-mbt
Any agent
npx skills add fizzbee-io/fizzbee --skill fizz-mbt
Clone the repo
git clone --depth 1 https://github.com/fizzbee-io/fizzbee

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for fizz-mbt

README.md
[![agentmods](https://agentmods.dev/badge/skills/fizzbee-io/fizzbee/fizz-mbt.svg)](https://agentmods.dev/skills/fizzbee-io/fizzbee/fizz-mbt)
Your own site
<a href="https://agentmods.dev/skills/fizzbee-io/fizzbee/fizz-mbt"><img src="https://agentmods.dev/badge/skills/fizzbee-io/fizzbee/fizz-mbt.svg" alt="Measured on agentmods" height="20"></a>
Per session 77 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,473 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00077 $0.02473
Opus 5 $0.00039 $0.01236
Sonnet 5 $0.00015 $0.00495
Haiku 4.5 $0.00008 $0.00247

Measured 5d ago against content hash f7f01d586a62, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fizz-mbt scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/fizz-mbt/SKILL.md · 296 lines

How it starts

The opening of the file, as written. The whole thing — 296 lines — stays where its author put it; the contents beside it link to each section on GitHub.

FizzBee Model-Based Testing (MBT)

FizzBee MBT generates exhaustive test sequences from a verified Fizz spec and runs them against the real system under test (SUT).

Examples: https://github.com/fizzbee-io/fizzbee-mbt-examples

Installation

# fizzbee (model checker)
brew tap fizzbee-io/fizzbee && brew install fizzbee

# fizzbee-mbt (test runner + server)
brew tap fizzbee-io/fizzbee-mbt && brew install fizzbee-mbt

Language Support Overview

Feature TypeScript Go Rust Java
Sequential testing
Concurrent testing ✓ (cooperative)
StateGetter
SnapshotStateGetter
Sentinel values (IGNORE)
AfterActionHook
OverridesProvider (fuzzing)
Playwright utilities

TypeScript and Go have the broadest feature support. TypeScript is the primary language for UI/E2E testing.


Workflow

  1. Write and verify the .fizz spec: fizz spec.fizz → PASSED
  2. Scaffold: fizz mbt-scaffold --lang <lang> --gen-adapter --out-dir <dir> spec.fizz
  3. Implement the adapter methods
  4. Start the MBT server: fizzbee-mbt-server --states_file out/run_<timestamp>/
  5. Run tests

Scaffold Commands

# TypeScript
fizz mbt-scaffold --lang typescript --gen-adapter --out-dir src/fizztests/ spec.fizz

# Go
fizz mbt-scaffold --lang go --go-package myapp --gen-adapter --out-dir fizztests/ spec.fizz

# Rust
fizz mbt-scaffold --lang rust --gen-adapter --out-dir src/fizztests/ spec.fizz

# Java
fizz mbt-scaffold --lang java --java-package org.example.myapp --gen-adapter --out-dir fizztests/ spec.fizz

Three files are generated per spec:

File Description Edit?
*_interfaces.ts/go/rs/java Role + model interfaces from spec No
*_adapters.ts/go/rs/java Stub methods to implement Yes
*_test.ts/go/rs/java Test runner wiring No

Read the full file on GitHub · 296 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 5d ago First seen · 296 lines · 77 tokens per session scan A f7f01d586a62

Subscribe to this mod's changes

fizz-mbt is a skill published in the GitHub repository fizzbee-io/fizzbee (347 stars, last pushed 10d ago), licensed Apache-2.0. It adds 77 tokens to every session and 2,473 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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