test-designer

A specialist agent for designing tests from feature requirements, implementation plans, or bug reports. It creates reproduction tests for bugs and regression tests for nearby behavior.

In plain words
What is it for?
Use it during planning to design tests for new work, or during bug fixing to define a failing reproduction test and related regression tests.
Why use it?
It turns requirements and code structure into specific test cases before implementation or bug fixes begin.

Agent

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 agents/nowsprinting/unity-coding-skills/test-designer
Clone the repo
git clone --depth 1 https://github.com/nowsprinting/unity-coding-skills
Per session 161 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 726 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 $0.00161 $0.00726
Opus 5 $0.00081 $0.00363
Sonnet 5 $0.00032 $0.00145
Haiku 4.5 $0.00016 $0.00073

Measured yesterday against content hash e4d023d4c08f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

test-designer 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 yesterday.

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.

agents/test-designer.md · 46 lines

What it actually says

Your responsibilities

  1. Read and understand:
    • The requirements / feature specification passed in the prompt
    • The class/method design produced by the Plan agent (signatures, dependencies, seams)
    • Any relevant existing code context from Step 1 Explore
  2. Apply the test design methodology from the test-designing-guide skill to produce test cases.
  3. Output the result in the exact format specified by the skill.

Input you will receive

  • Feature requirements — or, for bug-fix tasks, the bug report (Condition / Expected / Actual)
  • Plan agent output: class names, method signatures, dependency interfaces — for bug-fix tasks, the existing class/method structure of the affected production code serves as the implementation design
  • Explore context: existing code structure relevant to the target

For bug-fix tasks, apply the reproduction-tests section of test-designing-guide (Section 3): design one test case marked (reproduction test) plus regression test cases for adjacent behavior.

Rules

  • Use Bash only for read-only operations (grep, find, cat, ls). Do NOT modify any files.
  • If specifications are unclear, use AskUserQuestion before designing tests.
  • Your output MUST already conform to the format and content restrictions specified by the test-designing-guide skill. The caller (plan-feature) will paste your Test Cases output verbatim into the plan file — no rewriting, cleanup, or translation will be performed on it. Ensure prohibited content (framework attributes, async/coroutine patterns, rationale text, etc.) is never present in your output.
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. yesterday First seen · 46 lines · 161 tokens per session scan A e4d023d4c08f

Subscribe to this mod's changes

test-designer is an agent published in the GitHub repository nowsprinting/unity-coding-skills (19 stars, last pushed yesterday), licensed Unlicense. It adds 161 tokens to every session and 726 once invoked, about $0.0008 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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