blackbox-test-design

blackbox-test-design is a skill for Claude Code, Codex from Netcracker/qubership-ai-packages. It costs 195 tokens per session (6,294 once invoked), scanned A, original, Apache-2.0.

A method for choosing questions to ask a system whose behavior must be learned through its answers rather than its source code. It focuses on legacy services, vendor software, undocumented APIs, and reference systems used for comparison tests.

In plain words
What is it for?
Use it when porting or rewriting a black-box system, designing parity tests, or deciding which recorded behaviors need further investigation.
Why use it?
Each query may cost time, money, or a release cycle, and many questions reveal nothing new. This method selects questions likely to rule out incorrect behavior models and explains when to stop.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when porting or rewriting a black-box system, designing parity tests, or deciding which recorded behaviors need further investigation.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/netcracker/qubership-ai-packages/blackbox-test-design
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.

Any agent
npx skills add Netcracker/qubership-ai-packages --skill blackbox-test-design
Clone the repo
git clone --depth 1 https://github.com/Netcracker/qubership-ai-packages

Made for: Claude Code, Codex.

Its marketplace also offers this one on its own, as the plugin blackbox-test-design — /plugin install blackbox-test-design after adding the marketplace above.

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 blackbox-test-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/netcracker/qubership-ai-packages/blackbox-test-design/github.svg)](https://agentmods.dev/skills/netcracker/qubership-ai-packages/blackbox-test-design)
Your own site
<a href="https://agentmods.dev/skills/netcracker/qubership-ai-packages/blackbox-test-design"><img src="https://agentmods.dev/badge/skills/netcracker/qubership-ai-packages/blackbox-test-design/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for blackbox-test-design

Your own site · 80×15
<a href="https://agentmods.dev/skills/netcracker/qubership-ai-packages/blackbox-test-design"><img src="https://agentmods.dev/badge/skills/netcracker/qubership-ai-packages/blackbox-test-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 195 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 6,294 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00195 $0.06294
Opus 5.5 $0.00078 $0.02518
Sonnet 5.5 $0.00039 $0.01259
Haiku 4.5 $0.00019 $0.00629

Measured 10d ago against content hash cd36677c8452, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

blackbox-test-design 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 10d 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.

agent-packages/blackbox-test-design/.apm/skills/blackbox-test-design/SKILL.md · 378 lines

How it starts

The opening of the file, as written. The whole thing — 378 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Designing questions for a black box

Use this skill when the behavior you need is owned by something you cannot read: a legacy service, a vendor binary, a reference implementation behind a network boundary, a stand you can only send requests to. You hold a model of it (an executable spec, a port, a mock, a mental model in a design document) and a pile of recorded answers (goldens, snapshots, logs). Every answer costs something: a stand run, a person's time, a release cycle. The job is to spend those answers on the questions most likely to show that the model is wrong.

This differs from ordinary test authoring in one way that changes everything: the expected value is unknown. You cannot assert it, so a test here is a question, and its value is how many wrong models its answer rules out. A question whose answer every live model predicts the same way is wasted, however thorough it looks.

This skill decides which questions to ask. Turning a question into a test, with its level, its assertion, and its failure message, is test-authoring's subject, and so is a harness or comparator once its behavior is decided; load that skill too before writing any of them. Where the expected value can be stated, from a specification or from code you can read, the task is ordinary test authoring and test-authoring alone applies.

The sections below are techniques, ordered roughly by cost. Most projects need several of them, because each one is blind in a place another one sees.

0. Before anything: state the model and its provenance

Write down, or find, the model's decisions as a list: each place where the reference could have behaved in more than one way, the choice the model made, and the recorded answer that forced it (or "inferred" when none did). This list is what every technique below attacks. A decision with no answer behind it is a guess, and guesses are where the model is most likely wrong.

Settle the goal first: parity (reproduce the reference, quirks included) or intended behavior (reproduce what the reference was meant to do, and list the quirks as deliberate differences). The same answer is a bug to copy under one goal and a bug to fix under the other, and the questions worth asking differ.

Read the full file on GitHub · 378 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 10d ago First seen · 378 lines · 195 tokens per session scan A cd36677c8452

Subscribe to this mod's changes

blackbox-test-design is a skill published in the GitHub repository Netcracker/qubership-ai-packages (4 stars, last pushed today), licensed Apache-2.0. It adds 195 tokens to every session and 6,294 once invoked, about $0.0008 per session on Opus 5.5. 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 2026-10-08.

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